I don't know how the factory center box muffler works, that said: putting straight through resonators, which will be nothing more than glasspacks is not going to cut drone much, no straight through system will, we are talking about a long low resonation wave, these pass easily through straight through systems, V8 with more pulses, smaller pipe, longer mufflers, H or X pipes all help reduce the wave. The little V6 just can't use an exhaust that big without a significant drop in velocity. You need 2.25 or even 2.0 mufflers that are offset enough to allowthe wave to hit the inner tube of the muffler before it exits. Meaning larger offsets, smaller tube and / or longer muffler). Do a search on my exhaust post, it is all there. I have Magnaflo mufflers and note tht they are offset enough and the quad tips off set the exhaust enough that there is no or very little straight through view, so there is no long wave propagation out the back. Put it this way, AFAIK there are ZERO factory straight through systems. If it were possible to get sound / drone control with a much cheaper straight through muffler, the factory would have used them long ago.
IMO put you 2.5 or 2.25 glasspacks aka resontaors along the drive shaft you will be out the $150.00 and it will still drone. Buy two 2.25 mufflers with the baffle and you will be in heaven, choice is yours. Why are you designing a 400 to 450 HP system for a 250 HP car?
