@IslandMon and
@Jlaa it looks like I made a mistake in stating that these are backwards compatible.
I confirmed with Matt from Leistung Autohaus.
We never did the test fit of the new front section with factory resonator. The original design was to only offer the front section with upgraded rears.
That being said I am more than happy to do a return on these parts including shipping.
The other option which I am willing to cover the expense. Have a muffler shop
cut that pipe [on the Fleiben catalyst/test pipe assembly] 3-4” past that weld and replace with a smaller OD pipe that slips into the resonator.
This will allow the Oe flange to sit further back so it can fit further into the recess.
send me a copy of the invoice and I will refund the difference.
Third option
I can do the modifications here in CA but it would take two weeks to get these made and we exchange parts.
Return the old parts with the supplied call tag/box.