Ok i attempted to do my own research, but couldn't quite find what i was looking for. sometime this summer i plan on doing my own custom exhaust and i need to know the size of piping i will need. I'm looking at using stainless steel. possibly getting rid of the two cats right after the headers and clamping the new pipes in (to hard to get a welder in there). then putting two thrush glasspacks on the end. my question would be is that too loud? if so would keeping those two cats in make it not as loud? i don't want the car to too loud but maybe a little more then a nice rumble. im really just setting out to get a good performance increase and a really nice sound. so i just need to know what size pipe and if i should take out the cats. thanks!