I'm not sure if we're trying to keep this forum with longer, more in-depth threads, or, if out of respect for the original posts of threads, we should start new threads to avoid derailment.

I was going to post this in the GT wastegate thread, but I figured I'd make a new thread to not threadjack, and I thought good, short, searchable threads might not be a bad thing for specific questions.

Anyways, title says it all, would you suggest replacing the N75 valve with every new build?  The stock valve or the 'racing' version (I know the tune can be adapted for either)?  In my case, my engine only had 56k mi on it, but I'm thinking of replacing the N75 just so I have a completely fresh slate to start tuning on.   Thoughts?

I replaced mine just for the sake of it... I have the original old one still in the box as a back up.

New unit was bad though so I had to exchange it for another one which worked fine.

I have done it. No issues. You can always run N75 + MBC if you want.

I am running K04/K16 hybrids on an 00 S4.  Boost is around "O" in "VDO" on my gauge.

Driveability is great.  You can putz around town.  You can take road trips in the mountains with subtle increasing and decreasing loads.  It just spools faster and is more responsive.  There's no part throttle surging or any other issues.

The bottom line is the mechanical element can't be beat - there's no PID to tune.  Dial in your boost and you're done.  Very stable boost control independent of temperature/altitude/etc.

The downside is you can't just fire up your laptop and flash a lower boost tune if you're going to the track, but all I did was back off the MBC and count the detent clicks to lower the boost for the track with a few test runs.

I would recommend the hallman pro with the ceramic ball.  I had a turbosmart that I ran forever on my k04's, and after about 50k it would stick open occasionally (meaning unexpected low boost).

In short, it's not like an MBC breaks the bank, and if you don't like it you can sell it.