I think the general consensus among researchers is that backpressure does nothing for you. It is all about velocity. If the pipes are very small, it is helpful with low-end torque, b/c the velocity of the exhaust is very high. This helps to scavenge up all of the exhaust gases from the cylinders after the power stroke.
The problem is, people equate that with backpressure, which is wrong. If you have 4" straight pipes, and then they taper to 1" at the tails, you will have mad amounts of backpressure, but not much low-end torque, since the exhaust gases move very slowly through the pipes and this leaves a lot of exhaust in the combustion chambers.
So, ideally, on an n/a car with under ~200HP at the wheels, you want small pipes (2" or less for duals, 2.25" or less for single) with no cats or high-flow cats, and free-flowing muffs. This topic gets a lot of debate, but that is my understanding of it after reading a LOT of info from many different sources.
BTW, how are you going to pass emissions with no cats?
yeah maybe even smaller, I might go 35-45 jet, still decideding, yeah I already have 2/1/4 front to back, so would I even see a diff at all with no cats ebing backpressure prolly isnt going to go a problem? L8er
I wouldn't recommend it. I don't think you'll do any damage, however without cats you'll need to get something to fool the coumputer into thinking the car has cats. I forget what they're called, MIL eliminators or something? Basically, the after cat oxygen sensors will throw a SES indicating that the cats, which are not there, are performing below threshold value.
Did you have a custom y-pipe made also? The stock Vulcan is about 1 7/8-2", so if it's the stock y-pipe and you're just eliminating the cats, I don't think you'll see any gains at all. It's not a big-block Chevy, and the engine doesn't have the right type of mods to warrant a freer flowing exhaust.
And taurus8916, if you decide to take the cats off, what are you going to do with them? How much did you spend on these high-flow cats that you're willing to throw away? Just seems like a waste of money to me.