the smog pump has very little resistance so deleting it should result in no noticeable hp or tq gains.
also, without the air pumped in by the smog pump, the cats can get messed up (someone correct me if i am wrong). so if you still have cats, you should probably keep the smog pump.
if you have an off-road h-pipe with no cats, then the smog pump isn't doing anyway so no need to keep it then.