T28 won't hold boost

[mashloh]

have a S14 T28 and hks actuator set to 1.2 bar of boost.
I hit full boost around 4k-4.5krpm but after that it almost immediately drops to around 1.0bar and holds that till redline. ( I have a z32 maf, 555 injectors and rom tune)

Do you guys think it might be a boost leak? I read that the T28 should be able to provide 1.2bar (~17.5psi) of boost all the way to redline? Is this correct?

My vacuum line setup has one nipple from the throttle body T-ed to the fuel rail, the boost guage, the BOV and ending up at the wastegate. Is this too many devices hooked up to one vacuum line? Could this be causing me not being able to hold boost?

Thanks in advance.

[Flybert]

If you want steady boost, get a boost controller. The 1.2 bar is just a spike.

[rps13sr20]

Yup boost controller, even a manual one helps. I have the same turbo and hks actuator and boosting at 1.2 as well, it should hold better with a bc instead of just adjusting the actuator rod length.

[mashloh]

I do have a mbc, though i disconnected it thinking that having the adjustable actuator would be enough.... so when i set the mbc, would I still see the spike? and if it does still spike would it be ok to let it spike to 1.3bar and have it level off at 1.1bar or so?

[rps13sr20]

its normal for internal wastegate turbos to have their boost drop a little. And 1.2 to 1.0 isn't bad at all. I know a s15 t28 that spiked at 18psi and dropped to 10psi and he had an apexi ebc, but he had a stock actuator.

[mashloh]

so i connected the mbc again and it's still spiking at 1.2bar and leveling off at 1.0bar.... Do i need an EBC in conjunction with the hks actuator to hold a constant 1.2bar?

[unicoladron]

DUDE, you have way too many connections coming off one nipple. you need to go directly to the wastegate from a boost/vac source, and you should really go directly to the BOV as well. boost gague that is T'd between the throttle body and FPR is fine.

[unicoladron]

but yeah with an MBC that goes between DIRECT boost source and WG....obv