OK so before i wasn't holding boost, it would hold at just under 5 thorughout all gears. Now i added a MBC and changed the vacuum source(before-turbo, now-intake mani)
So in D3 when i floor it on the highway, it jumps past the 6psi a little then drops down to 5, get up to xxxMPH shift to D4, i see the boost gauge holding at 9psi.
Whats wrong with my damn thing, i just want to boost 8pounds max, and hold 8pounds

 

what kind of MBC is it... sounds like you may be experiencing some boost creep.

whats your setup?

 

probably a DIY or eBay cheapy based off of a grainger valve if I had to bet. If you are using one of those, take it off and get a decent one like blitz, greddy, or apexi. sounds like you migth be spiking a bit and/or have a leak somewhere on the MBC itself.

which is common with the ball/spring styles that the people try to sell.

what turbo kit? if it's a greddy kit, they aren't known for their tolerance of being boosted past factory specs due to the shitty wastegate mainly but the small size of the turbo is another factor.

I wouldn't be manually shifting that transmission to often in boost like that on the highway unless you enjoy watching the bands fly out on the road.

 

its a greddy 15g in a LS. 2.5" dp-back to muffler, tyrus ic
as for the MBC its a DIY ball spring. I had a post before where it won't hold boost too when the wastegate vacuum was connected to the turbo, then i switched it over to the intake mani, same results, then now added the MBC and only 4th is hold at that high.
as for shifting on the the transmisson, i put it in d3 before i gun it, then i shift it up later on

hey stackz what are you using to control the boost?