P0172 and chugging

[jhubbz]

Ok, So every once in a while I will get a p0440, which I've always just cleared, because I never thought it was a huge deal. For the last couple weeks, when I hit the gas, it won't go right away, but at about 15% throttle, it will finally jump in. I read ion's thread about a sticky throttle plate, which made me check mine, but that wasn't the problem.

A couple days ago, my Trac off light came on while I was on the highway and my Ultragauge immediately threw a P0172 at me (System too rich). It went off after a day, but I wouldn't be surprised if it came back.

Just checked my spark plugs and they look fine.

Of note: I have MSD coils and a 2.4 with a CAI.

Anyone know what the problem could be? I'm thinking my cat is really starting to clog, causing backpressure, but would like some input.