cutting only 2 cats?

i think it would only help the sound, don't konw how much of a seal you could get with interchangeable pipes, sounds like a good idea though

the upper "cats" are "precats"

i just read a little article.. the precats are used for coldstarts and burn off the excess fuel while the main cats are warming up.

i don't think that helps at all, BUT although not knowing where you live, it might be possible in your state to completely eliminate the upper "precats" since those are a huge restriction