Possible Cat issue again?

I have an 02 Grand Prix GT and got my Cat replaced by a shop (actually paid didnt hear about the recall for my car on the cat on 01's and 02 gt's or w/e). Anyhow when I accelerate in my car WOT it tends to sputter a bit at around 4-5k RPM's. It'll back down for a sec then kick back in. I'm guessing this has to do with the cat possibly being clogged again? Im guessing they replaced with stock cat and it was awhile ago (probably 2 years ago) when i had it done. So I'm wondering what the problem would be. I also have the Bosch Platnium Plus plugs would that be something to do with it? I have no idea. It's been real subtle for a long time, like i'd notice every once and awhile but now it seems like every day if i go WOT it will sputter a bit.

Also I have another possible symptom if I just sit there and rev it for a bit in park or neutral the exhuast will sometimes pop or almost cackle when I rev it even lightly sometimes itll do it.

I'd do a tune up. Including fuel filter change and maybe some seafoam through the injectors.

Whats all involved in a tune up?

plugs, wires, filters etc etc.

BTW ben i started my fuel filter and jacked up the car, then said "screw it" its so cold dont even waste your time for now, tires plus charges over 80$ for just a fuel filter, and my fuel filter sitting in my room was 15.99, even so, when are you going WOT in this weather lol, just curious

Make sure you don't strip the end of the fuel filter trying to get it off, if you do, have fun, it's a PITA. I'd take it somewhere to have them do it so if they screw up it is their problem. That and they have the proper tools for getting it off.

that is a good point, but i mean, im not gonna do it till spring

100mph stoplight lauches LOLJK

mine cackles pretty good
http://www.youtube.com/watch?v=cmWUrPl1JYY

The popping noise you hear in neutral/park is the rev limiter, stops your engine from revving to high when your not driving, totally normal

My mother car was doing the same thing and when I changed her spark plugs, all of the sputtering and hesistation went away and is back to normal. So maybe do a tune as everybody say, good luck.