Sometimes my car goes into this, slow mode, when i hit the gas it accelerates very very slow and sounds louder than normal. I still boost normal. But when I cycle the key once, shut off then on, it runs perfect. Its been doing this once in a while for a few months, but now it happens at least once a day. Has anyone heard of this before? I have a s13 w/ redtop sr20det stock, fmic, 3 inch catback.

exhaust leak...

i checked for an exhaust leak, and everything is tight. just replaced turbo and manifold gasket too, last month. The car resets back to normal if i shut it off then start up again.

sounds like an ECU issue.

yeah open it up and check for water/rust/corossion/damage. My brother in law had a similar issue.

check for vacuum leaks aswell

When you say "louder than normal" does it sound like an exhaust leak? Or does is the engine revving higher than it should be? What exactly sounds louder?

You said it's boosting normally, but are you still accelerating faster during boost or is it bogging down more?

From what you've already said I'd either guess you've got some rust floating around inside your plumbing, or your ECU has the hiv. Like he said, you could probably open it up near the cat and check if you have a family of mice living inside your downpipe.

ive had that same problem happen to me before. i never really fixed it but it just hasnt done it in a while. it sounds like the eact same thing.
imagine the souns of your car when you are going fast and up to like 5k and put that sound on when you are going slower and trying to accelerate. i guess that is the best way i could explain it.