I have had my car back together for about a week now, and i've been slowly adding boost back in, I started at about 14-15psi and slowly turned it up to about 20, but after the last time I turned up the boost (to 20) when I'm at WOT the boost fluctuates rapidly between about 15-20psi, just shoots back and forth real fast, what could the problem be? I think it has like a 6psi spring in it, its a knockoff external wastegate, could the spring be too small for the amount of boost i'm running?

 

try a bigger spring...pretty sure the rule of thumb is not to go over double the spring

 

your mbc working properly?

 

I will try a bigger spring, the MBC is homedepot style but has worked great until I went past 18psi.

 

I def. agree, I'd say get a 14 psi spring and go from there

 

sorry to bring this thread back but the problem resurfaced.

I put a 1 bar spring in it and boost holds rock steady at 15psi, now when I turn the boost up (still my homedepot mbc) it still flutters like crazy between 15-25psi. I just purchased an electronic boost controller but its not here yet so we'll see if that helps.

 

Post a picture of your wastegate installed on your manifold. I've seen this with some "orientation" problems.

 

does it sound like this?

http://www.youtube.com/watch?v=nCj6Spwl1CU

 

Seems like this is what you are describing what size turbo are you running?