T28 boost issues

[mlhiser]

I'm having some issues with my sr wondered if y'all could help.
Previously replaced a cracked manifold and put in all new exhaust gaskets. Before manifold cracked, was running consistently at 14lbs (s14 non bb t28 and greddy profec electronic boost controller). Manifold cracked, only boosted like 7lbs max. After I fixed it it ran fine but started pushing 20lbs consistently. It worked fine so I didn't mess with it for months then it started doin this thing where once you hit like 10lbs of boost it would cut out and backfire and wouldn't accelerate similar to conditions of a fuel cut. I figured out the wastegate actuator was shot thus allowing me to overboost to 20lbs for so long. So I replaced the actuator and now the boost bobs up and down between 10-14 lbs on the gauge while accelerating. Was thinking maybe the maf or injectors or fuel pressure regulator, what do you guys think? Anyone ever experience any similar conditions? Just looking for ideas here so I don't get buying a hunch of parts that don't need to be replaced

[brndck]

Sooooooo you were running 20psi on a t28? My first guess is that you ran lean and caused engine damage.

Start with a compression and leakdown test. Check your plugs too.

[mlhiser]

What engine damage would have been caused that would result in my car boosting as it is? Nothing else is wrong, I daily drive it the way it runs, it only encounters this problem under WOT. I can hold the boost at a consistent point like 7lbs with no problem, it only "bobs" up and down at wot. It doesn't seem like mechanical failure IMO but more of a fuel delivery/air intake issue. And as far as leak down test, if there was excessive blow by it would pressurize the crankcase and lead to oil in the intake, correct? I have a catch can and it doesn't have a drop of oil in it.

[mlhiser]

Compression was checked before cracked manifold and was good about 155-160psi. Plugs were one of the first things I replaced before I fixed the wastegate and they were not disturbingly fouled. Just a little white residue from using a few bottles of injector cleaner and octane booster.

[bmxer882x]

Sounds like a boost leak to me. Check your couplers/bov

[Fuego]

You should do another compression test since you made it worse after the initial test. That much boost on stock MAF, injectors, and pump I promise you were running lean. Running lean means you were running hotter and may have damaged the pistons and/or rings and you could be getting blow by.

That all said, you can do normal maintenance when your SR isn't acting right. Clean the MAF and injectors, check for vac/boost leaks, check your fuel pump and filter, and the actuator if you got a cheap one.

Lastly, stop using octane boosters. They are 100% worthless.