World's most frustrating boost issue
 

I had my car for a week, installed a softronics tune that was making 1.1 bar, had the engine out for the waterpipe issue (new clutch, all hoses, etc) and then it was only making .7-.8bar and the diverter valves (710n's which had less than 50 miles on them) were honking.

The mechanic put vacuum to the valves and they held fine. He put a smoke test to the entire system and didn't find a leak. I bought new 710p's just incase I got a bad valve the first time. I went ahead and told him to put the new ones on anyway, he replaced a few small dried out lines and checked other connections but no smoking gun.

I drove it out and it was making 1.1-1.2 bar with no honking sound so I chalk it up to a bad DV and think it's fixed.

A day later it is only making .9bar consistently and feels much more sluggish. Sometimes it makes 1.0 in 4th or 5th but drops to .9 after 500-1,000rpm and holds there.

I'm completely beside myself asto what the issue could be. Could the diverter valves have gone bad yet again?!

There was also a decent amount of blow by in the pipes when we did the work so also cleaned the MAF sensor, I'm not sure if that could have affected the pressure or not.

Anyone have any ideas?

I'm overly frustrated thay the new car I paid a lot for and immediately put $5,000+ into wont perform properly!

Advice is greatly appreciated and needed

could be a 30$ check valve cracked. its my favorite semi known yet fairly common boost reducing issue.

I like the idea of a $30 fix

Where is the check valve located?

instead of the smoke test, try doing a boost leak test, you will find the leak easy!!

on top of the plenum. just search for a thread of the intake parts, it'll be there with a graphic. it's #16 iirc? there are two actually. and yes to pressure test. agree that smoke tests are all but useless on these

boost leak test is only way out, you can buy a kit from 911tuning

Made my tester from parts at Lowe's for 12$.

also to add.. if you even suspect the maf is failing? and there are no codes pending or outright? then cleaning the maf is a highly inconclusive way to try to eliminate that as a contributant to your issue(s)!

cleaning mafs is as hit or miss as anything can be. also as most here suggest, you need to eliminate any possible vac leaks and the only proper way to do that is pressure testing. its rare NOT to find leak(s).