Originally Posted by willwren
There are no CAI'* or Cat-Backs for ANY year of Bonneville.
For the most part, you don't want a cat-back. Our exhaust is free-flowing mandrel-bent stainless steel. Change the mufflers alone for a change in sound, they won't provide any power gains.
Ever cut apart an OEM muffler? I have. There is plenty of restriction in there. Most are a minimum of 4 chambers. Some of the GM trucks are 6. OEM mufflers (as well as most componentry throughout the car) is designed with multiple objectives in mind. They include power, economy, sound deadening, durability, serviceability, etc. This jack of all trades, master of none approach leads to some obvious areas of improvement.
The plumbing in our car is ok and free flowing as you mentioned (I was actually pleasantly surprised by this when I had it up on the rack) which is why I'm not touching it. If I were to do a blower or internal engine mods, that'd be a different story and I'd go 2.5" at a minimum. It'* not so much about them "making horespower", but rather them allowing better volumetric efficiency which when combined with the "uncorking" of the intake side also, works as a system allowing that big air pump under your hood to be more efficient. This translates into easier acceleration from less RPM'* needed to obtain that same level of acceleration. This results in better economy as well as allowing the engine to spool up quicker when needed which allows the engine to be more efficient in power making. It'* not about the individual pieces, rather the system as a whole.
Trust me, I've learned a few things over the years as a technician and modding a few vehicles!
But sound is the other reason I'm doing it.