noise at ~2800 RPM
 

I have a straight downpipe for now on my '87 TII and haven't done much besides pull emissions and port my wastegate. Most the other things I've done are just for maintenance. When I reach 2800 RPM the noise the motor makes seems to double, and stays that way beyond 2800 RPM until you drop below 2500. What I'm suspecting is that my tach is low by 1000 RPM and what's happening is my secondaries are coming online when I think it's only at 2800 RPM. Does that sound right or does it sound like something else? btw I get the 3800 RPM hesitation once in a while, and when that happens the tach actually reads 3800 RPM, so I'm kind of confused about this. The motor doesn't stumble or anything when the noise increases, but it's a distinct and consistent issue. Any ideas? Is this because of a problem?

I doubt your tach is off by 1000 rpms, are you idleing at -1750? You could be developing an exhaust leak, common problem in the tII. I've got one, sounds like crap!

I mentioned I only have a straight downpipe right now, so I don't see how it could possibly leak. Also, this only happens at light throttle acceleration, the noise increase either doesn't happen or isn't noticeable when I'm accelerating quickly.

the leak I'm referring to is actually between the turbo and the exhaust manifold, but that noise is hardly noticeable unless at idle.

I installed a new turbo/mani gasket, too