pickup problems

i have a 93 LS 400, and its pickup is very inconsistent. sometimes it will accelerate very good, and spin the tires, other times it feels like i am driving a 4-cylinder. i am running premium in it (which is recomended) so i do not believe that is it. also, it seems to have better acceleration when its cold, but it also does it sometimes when i've been driving for awhile. any suggestions? i think maybe clogged injectors, but i'm not sure beyond that. thanks

kevin