On my cars's install both down pipe to midpipe and midpipe to muffler connections had to be welded. (maybe because I did not tighten the sleeve properly)

On the second install I did on my buddy's x5 the buzzken midpipe to down pipe connection would not fit more than about 1/4 of an inch even after cuting up the midpipe on both sides with a sawzall to get it to open. the pipe just wast round and required a weld. the mid pipe to muffler sleve however did seal properly after over tightening it.

so yes who knows what yours will look like the it's kind of a rough fabrication process they have. maybe yours fits like a glove who knows.

The aspect of our tune (DUDMD) that is significant IMO is that I have removed the passive and active tank without limp or CEL's and I do not think anyone else has done that.

even some guys at the e90 forums are looking for resistors and gimmicky stuff to remove their tanks after being tuned by major name tuners. (I believe BPC )

it's significant because when your tank goes bad you go into limp mode. and right now the tanks are free under warranty but 100k miles down the road when it does go bad it probably wont be. they are around 1200 each new. My used active tank sold on ebay for $650

another aspect of a tune that I have seen others struggle with is that some people have gotten misfires with no CEL and no codes logged. this is a huge problem as some tunes appear to numb out the ECU by routinely deleting codes that come up.

so when you have a injector issue or some weird problem later you will have no choice but to send the ecu back and run a detuned or mild version of the tune just to get the errors to log.