Hello,
I just bought an 04 GTP and of course 3 days later it now sputters VERY badly when pushed at full throttle, which I've done less than 10 times, but the 6 or so yesterday and today have got progressively worse. Seemingly zero problem at about 40% throttle and under, but if you floor it, it bogs down almost immediately. I was thinking fuel filter or cat, but since I'm new to these, I thought I'd ask a community of owners first! Thanks for your help and I hope to help others here one day once I get to know this car better.