Dave and JC, I have in this past year spoken with both of you about the fact that I am the owner of the header/exhaust system to which you refer. It is now 7 years since your above comments, but I thought I should mention this info here, just to complete the discussion of it on this thread, which I am just reading for the first time, I believe, at least from the beginning.
Since you both already know, I will say for everyone else that when I bought this car in 1999, it had a Renntech rear muffler assembly, which rattled. Someone I met suggested I give this locally known craftsman named Herb Gebler a call to see if he could weld/repair it. Herb's business was racing headers and exhausts and was called Gebler Racing Headers. Herb made the case it would be better just to let him make a new rear exhaust piece in place of the Renntech one. He persuaded me to let him ditch the rear muffler entirely in exchange for stainless rear pipes with spirals inside them. They made the car a fair bit louder and sound really good.
Herb then convinced me on principle (not because he was an expert on the Mercedes 119 engine or the 500E OBD 1 ignition system) that he could in principle make an entire system from headers on back that would, in combination with adjustments to fuel and timing in the ignition system, create a HUGE amount of more horsepower. Herb really and truly believed this based on his experience with road cars through the years.
Unfortunately, only after Herb had custom made the headers and exhaust, building them on the car, did we discover through the tuning shop, Intersport in McLean, VA, that the car had an OBD 1 ignition system, meaning there would be no way to adjust the timing, meaning the entire exercise was likely for naught. This was a MAJOR FAIL for Intersport, whose owner, Charlie Murphy, was a highly recognized and on the spectrum brilliant Porsche expert and engine rebuilder. Charlie never considered the idea that the car was not properly tunable and did not do his homework prior to Herb's building the exhaust.
Nevertheless, once that was realized and after the exhaust/header system was installed, Charlie went ahead and worked with Autothority, a very well known Porsche chip tuning company in Northern Virginia owned by a supposedly nationally recognized chip guru named Al Collins, to make a fuel (or EPROM) chip for the car with the new exhaust. I went with them to Autothority to have an EPROM chip programmed with the car on the dyno.
In the next couple/few years, I burned through two or three sets of catalytic converters and eventually blew the engine, taking the car into my service company with what turned out to be likely a bent rod (from the banging noise which rose an fell in tempo with the engine rpms) and two or three badly scored cylinder walls. Fortunately, Potomac German had a 50,000 mile 500E engine they had just acquired at that time from a t-boned 500E, and I bought it from them for $5,000 -- much cheaper than the $13,000 I was being quoted for a rebuild from a well known Mercedes engine rebuilder or the $20,000 Mercedes wanted for a new one!
Needless to say, after this entire experience, I blamed the aftermarket exhaust and chip and replaced them both with the original exhaust parts, including a new Genuine rear muffler from Mercedes. I also blamed myself, as I knew very little about cars at the time and just put myself in the hands of others, who dropped the ball at great learning expense to/for me. I still have the headers and exhaust in storage.
It was not until this past year, in speaking with JC, Dave, and others, that I realized that the exhaust was likely not the culprit but that the chip was. All my unfortunate experiences could not be explained by headers and a more free flowing exhaust but could be explained by a fuel/EPROM chip running too rich. So, it seems the chip was the problem, not the exhaust.
Regardless, while I will not say I lost power, which Dave seems to remember incorrectly, I don't think I gained any either, at least not that my butt dyno could tell, and there was never any proper dyno measuring done before and after.
In reading this thread just now, I thought to look and see if Herb Gebler, a gruff hunting and fishing old school redneck sort of patriotic American with a heart of gold underneath, had ever created a web site for his business (Herb wasn't exactly the internet type in 2001). In my search, I discovered a legacy web page devoted to him. Apparently, he died in 2011. Very sad. He was a good man. One of the comments on the page said Herb built headers for Richard Petty, which if he had told me I had forgotten. Here is the page with a couple of photos of Herb:
	
	
		
			
				
			
			
				
				View Herb L. Gebler Jr.'s obituary, send flowers and sign the guestbook.
				
					
						
					
					www.legacy.com
				
			 
		 
	 
Last fall, in exchanging PMs with JC, I note that JC made the following observations about the exhaust and headers after viewing detailed photos of them. (JC, I don't think you will mind if I share the following. If you do, please let me know, and I will delete):
"That's race car status right there.... I commend the builder utilizing pre-bent mandrel bends and pie cutting it all into an exhaust.
There are a lot of things i would have done differently, and with the access to CNC benders here in California i should be able to replicate that and clean it up by ten fold.
But anyone that would use something like this would not appreciate it because the sound would simply be too loud. I doubt the car would pass the 90db sound limit in most tracks out here in the west coast.
But the craftsmanship is top notch especially since its all done by hand."
The sound was very loud. No question. It was also a truly unique sound. Much nicer, frankly, than any of the E500E modified exhausts I have heard here on the Board or on YouTube (although certainly in person they would have sounded a bit different). Herb's exhaust and header sound on this car was cleaner, lower, more throaty, more powerful in an old school way, more manly, if you will, less metallic, and smoother. Believe it or not, I received many many compliments on it.
However, I will confess the drone/resonance inside the car got pretty old after a while -- made me keep the music up loud 

 I'm sure the H&R lowering springs I had on the car at the time (came installed when I purchased the car) didn't help -- creating less space underneath for the sound to travel outwards and instead reverberate back into the car.
Anyway, overall it was a beautiful sound. You'd have to hear it to believe it.
Here again are images of the exhaust, both on and off the car:
Index of /images/M119/exhaust/500E_custom_exhaust   
Godspeed, Herb.
Jamie