'94Z A4, 118k. Mods list in signature. Car is tuned but still isn't right, runs really rich but has been fine for the rare times I drive it over the last year. If I drive it long enough it eventually starts to stutter and bog, but today it started surging strongly after about 5 minutes of driving. Worth noting that it throws no codes for any of this. Opti and waterpump have ~8k on them replaced a year or so ago. The only real problem otherwise is an annoying header leak. EGR deleted and removed...im trying to think of everything...O2s are a little over a year old.

It will bog really bad followed by lurching forward really fast. It goes back and forth between these two at about 5 seconds each. It didn't appear to be as evident @ WOT but it was still noticeable even with cruise on @ ~35. I turned the car off, waited 2 minutes and it was gone when I restarted and took it for a quick spin but I'm sure it will be back when I try to drive home from work. Thoughts?

 

might have damaged an o2 from the leak in the header