Roush 427r only made 400whp :(

[wanab5150]

Not sure what direction this post is going but to answer the side pipe question....I use 3 inch Chambered exhaust pipes, no packing with the open end of the louvers inside facing the engine. The muffler part is the same size as stock. I also have headers that fit the Roush/AFR large port heads...Superformance makes 2 sizes.

One for standard ports and another for large ports. If you have small port headers on large AFR heads it will do nothing to add inch exhaust because of the choking at the header.

I have the large port headers that fit the AFR heads and the 3 inch mufflers. With all the torque it's hard to tell the difference at low rpm and 1st or 2nd gear. But, when you hit third the thing just goes nuts through the rpm range. It was always scary at high speeds but now third gear to 6000 rpm is unbelievably scary.....I love it.

My one and only time at Infenion raceway (Sonoma) I turned an 11:87 on 315 x17 Goodyears....junk in the trunk and forgot to lower the tire pressure.....Off the line its hard to control and spins through 1st and will in 2nd if you don't ease out the clutch and monitor the throttle....then wide open 3rd and 4th.......Wish I had a set of drag radials to really see what it will do......Also for info. 770 Holly street Avenger...Go with the Chambered exhaust if you want your HP back. My stock mufflers were 1 7/8 inside dia.