I had a plugged cat and drove it for about a week until the bucking and stumbling got too bad to drive and I took the cat out. Drove fine when it was originally taken out. Fast forward ~2 months and now the car is detonating in 4th-6th gear, only when 1/2 to wide open throttle. I'm thinking carbon buildup is causing this, but the car was tuned and leaned out when the cat was removed. I don't have anything to see if it's getting enough fuel or what so I'm trying to rule out simple things first.