the best plug is the acdelco 41-110. and your cats don't get "clogged" after 140 thousand miles, they can get worn out and if you hit something you can shatter the catalyst. removing them is really not worth anything performance wise. it will make things louder though. you won't notice the sound much until you put a good exhaust on it. magnaflow is about the best you can get. PLEASE don't get bigger than 3 inch tips. that sounds worse than a fart cannon...

 

LOL no fart can over here. And what does this plug go for a piece???? $6???

 

something like that. they are like 7 at napa which is where i bought mine. they are better than the factory plugs and should last you just as long. you don't want to go cheap on plugs or else you'll go through quite a few sets.