Overboost issue

[andyb16]

I got my twosrus mbc and fcd put on today and have a strange overboost issue. The car boosts fine (set at 15) if I'm in the right gear, like if I drop it into 3rd at around 45-50 mph, but if I'm in 5th at say 60 and floor it, it'll boost up to 19 or20 psi. If I let off, it'll stay at, say 17, until the revs get up to where they would normally be for WOT acceleration in that gear, then it goes back to 15.

The instructions for the mbc were followed correctly, everything double checked, tvsv disabled, etc...

'92 stock ct-26 Mods-EMS 3inch downpipe, HKS Hi-Power exhaust, HKS Super Mega Flow intake. Just put the d/p on tuesday, wasn't doing this after I put it on, boosted totally normal until the mbc. When it goes over 15, I can hear what sounds like someone whistling coming from what sounds like the turbo area, I hear it in my right ear.

No boost leaks afaik, boost gauge shows 20 hg in vacuum.

Any suggestions? I'm gonna turn the boost down tomorrow and see what it does, but I really want to run at 15 since I've had a taste

Thanks in advance!

Andy.

[TheEngineer]

have you pulled all the way through third to make sure it maintains a max of 15psi. That is ussually the gear you test in. Its pretty strange your only seeing it overboost in 5th at lower rpms no less.

My first guess would have been a problem on install but you squared that away. Possibly a wastegate issue but i can even see that since you arnt having any problems in 3rd.

[andyb16]

Holds fine all the way through 3rd. I don't get it.

Could it be that there isn't enough pressure on the actuator to open the wastegate until higher rpms?

[andyb16]

I messed with it some more tonight. I took the screw all the way out of the mbc to run off the wastegate and got no spike. Ran at 10 psi rock solid, which is were it was before I put the mbc on. When I put it back in, it took quite a few turns to change anything, and once there was a change, it was up to it's old tricks. It was either 10 psi w/ no spike or 15 psi with spike city.I'm totally at a loss here.

When I had the screw out, I did notice it would only go 7psi in 5th, but I wasn't going very fast so I don't know if it would've crept up to 10. With it being saturday night, I didn't want to push my luck and get pulled over. I'm going to triple check everything tomorrow to make extra extra sure it's hooked up properly. Would this maybe be caused by the hoses being switched? We ran them in throught the firewall in behind the driver's seat, but marked them to keep them straight. I guess it's a possibility we still got them backwards, would that cause my problem?

Any help would be great, as this is really not my area of expertise. Thanks!

Andy.