engine sputtering on warmup? and lack of power?

I have a 98' M3 supercharged with every bell and whistle possible and I have been haveing a problem on warmup where the engine starts to sputter. I think its running lean but I am not sure why or if there is another problem. It has a new fpr and fuel filters so I know thats not the problem. It also doesn't matter if I have a full tank of gas or not. it helped when I poured in a bottle of injector cleaner (techron) but didn't solve the problem. It will start sputtering at about 3k rpm. I just had my head gasket replaced because it blew (probly from the heat and the 8.9 psi at 7.2k rpms) but since then have lowered the psi down a bit...could this be the gasket showing signs of failure again? Help would be appreciated. Thanks

~Matt M.