boost ? please help!

[heater]

i have just put on hard i/c pipes and a 1st gen bov i have my t25 on and a mbc. this is the problem when i put 3 turns on the mbc i boost up to 15 and fall right back to 12 real fast and hold 12 till high rpms but if i put 5 turnes on the mbc i boost to 17-19 adn fall right back to 15 real fast???? i can figure out why it will not hold 15 with 3 turns? also should i set it to hold 12 or 15?

 

[cool_g_83]

The reason your boost is falling off is simply due to you still having yout t-25. It cannot produce enough flow to keep up with the engine at higher rpms, hence why it drops off. MBC seems to be working good, so don't worry about that.

 

[oldman]

The reason your boost is falling off is simply due to you still having yout t-25. It cannot produce enough flow to keep up with the engine at higher rpms, hence why it drops off. MBC seems to be working good, so don't worry about that.

Close but the problem is not boost falling off, it's the typical T25 spike then settle. Three turns is probably 12psi and 5 turns is 15psi so the mbc is working fine. I would however strongly suggest performing a boost leak test since you have done work to the intake tract.