loud ticking noise upon acceleration

I have read similar symptoms discussed here but usually on cold starts and noise tends to dissappear after a few minutes. I am concerned though because this ticking definitely gets louder "under load" and does not go away.
Does this sound like simply noisy lifters or something more serious? The car seems to run well although, I think it has lost some power in the last few years. By the way, it is a 2000 3.4 Alero. Could it be carbon build up too???


Thanks