low vac but no boost leak?

[Big28 2gFWD]

ok this is a quickie...vac is at a consistant 15.5 but occasionally drops to 12 (which is usually where my car stutters and stalls but im also having some auto tranny probs right now so its hard to pinpoint) but my boost stays at a consistant 21psi where i am set to. i have not found any boost leaks to date...so any ideas? thanks

 

[Defiant]

Where are you tapped into (don't use the throttle body) and are there any kinks in your sender line?

 

[Big28 2gFWD]

both the boost gauge and the boost controller (greddy profec b) are tapped on the vac line closest to the driver's side on the intake mani. also i might add that im running an open atmosphere b.o.v. with a stock 2g mas, ive been running this for 3 years now and never had a problem until recently..

 

[oldman]

i have not found any boost leaks to date...so any ideas?

Was that the results of a real pressure test? If not, I suggest doing one asap. At least turn down the boost until then, you could be over working the turbo to maintain that 21psi if in fact your low vacuum is cause by leaks.