I brought the 88 Callaway twin turbo in for the new Dynomax ultra flow mufflers today and here is what I have to report. First off I did not have to remove the main cat because it was removed by Callaway when the car was built in 88 and replaced with a straight pipe. We also discovered that Callaway removed the original pre cats an installed their own low restrictive pre cats.Now as far as the mufflers go the Dynomax look exactly like the style of the original GM stock mufflers except the are a bit beefier and are 100% high polished stainless steel for a MUCH better appearance.I removed the original Y pipe and had a Y pipe with a larger diameter and a better configuration for exhaust flow installed.THAT'S IT! Results? A clean crisp low rumble that is AWESOME!