Some basic maths for you guys.. The cross sectional area of a single 3" tube is 28.3 inches square, a single 2.25" pipe is 15.9 inches square, 2 of these equals 31.8 inches square. The standard exhaust, twin 2.25" pipes has more cross sectional area, and hence flow potential than your single 3" pipe!.. If you are looking to create a flow restriction then go for it! PS.. a 3.5" pipe has area of 38.48" square, so I wouldnt bother with anything less than a full 3.5" system, which is what I have on my car.