I have APR chip, bailey motorsport dv,N75 race valve, samco intercooler piping, full 2.5'' exhaust from the test pipe back. My car will only spike 18ish and hold 15psi, it used to hold 18 and spike 20psi. This is in 50-70 degree weather. Also the boost drops off to almost 5psi past 5k rpms. Im thinking maybe try putting the stock n75 valve back in?

 

Your'e talking about a difference of a couple psi. Still sounds normal. Dropping off bellow 10 psi is normal for the turd sized turbo past 5k rpm's. Everything you descirbe sounds normal, but you could try putting the stock n75 back in. You'll def notice quicker spool up with it. The race valve is more smooth, but the stock valve will feel like insta-boost when you go back to it. I've gone back and fourth several times and thats the conclusion I came to.

 

okay, I am just making sure its normal on stock turbo for it to drop boost so much. Time to upgrade soon!

 

Figured out my problem while I was at the track last night. It was 60 degrees out start of the drags. I ran a 15.6 my first run and there was a dramatic loss of boost. Next run was a 15.5. I know my car is faster than that, so I noticed my service oil light had been on for quite sometime I forgot to reset it. Reset that, made another pass and hit 15.1 and my boost was fully kicking in like it should. Next run was a 14.83@93mph. Time to start my turbo swap so I have some fun while I build the VR6-T

 

could also be that heatsoaked side mount. its called a one time use intercooler for a reason.

 

i dont think a service oil light would cause performance problems...

 

Nope because it ran better times as soon as I turned off the service oil reminder. And it was 59-60 degrees out.