A while ago my a4 dropped 2 coils causing raw fuel to dump into the cat and melt the catalyst. I replaced the cat with a test pipe and the car runs like crap. I pulled the plugs and it looks like it's running lean which makes sense with the test pipe and stock tune so I'm looking for an inexpensive tune to fix the lean condition without other mods. I would consider an air filter or something reasonably priced in addition to the tune if it's needed to fix the lean condition but my goal is to have the car run well, not necessarily to make more power.

What would you suggest?

 

I believe my torque converter clutch is going out. Previously I've experienced shaking at cruise in OD, researched and found the Torque converter control valve is common to go bad on the 4l60e transmission, so I put in a transgo shift kit that supposedly solves the issue and eliminates the clutch pwm apply function. I also put in a bottle of lube gard and Dr. Tyranny shudder fix. Problem is still there after the install, but not as pronounced. It's a work van and I live on pretty flat land, so I'm dealing with it. On Hills the shudder shows up and I just kick it down to 3rd and it goes away.

 

Mine actually turned out to be the cv axles. I replaced both and the vibration is gone.