If the cat is getting clogged you will deffinately notice a difference, otherwise a highflow cat will give you the same benefit as a straight through setup about 5hp and With a highflow you won't have to ever touch it. Don't cali trucks have 2 O2 sensors anyways?

I saw someone had posted a cheep highflow cat here before, I think it was like $75 or something like that.

(aka suprathepeg, aka Sean)
89 v6 SWB truck "BLACK BEAUTY" EB valves, P&P head 30 over.
95 FZJ80. Lifted. locked and rollin on 33s (my dream machine)