Hi all, I have a 91 golf gl. I recently replaced her exhaust with the dual downpipe system and she was a dream to drive for about a month. Recently, however, she has begun hesitating on accelerations from idle and she sounds like an old truck when accelerating (I can hear the individual cylinder explosions well). Her power has also dropped significantly.
I think the o2 sensor is fine. I replaced it 10-20k miles ago, there was a bit of a struggle getting it off the old manifold and it is now located on the cat. She drove fine for ~1 month so I don't think this is the problem.
I was under the hood the other day searching for the exhaust leak. When I turned the throttle the engine would putter down for a second then rev up like it's supposed to shaking violently. I held my hand around the manifold/dp area right when I started it up and didn't feel any puffs, only some slight wisps coming from the dp/cat junction. I've read a few threads about the flex joint on the dp going bad, my dp is used but looked in good condition when I put it in.
I'd appreciate any help on resolving this matter.
thanks,
-Matt