I Know for a fact the the Magnaflow does not a have a resonator. The resonator will make the exhaust a little quieter, but then the the Magnaflow comes with a silencer. Also the Magnaflow is cheaper.

 

You can order it with or without. I recommend getting it just because the price is the same and it bolts in. I keep it, damn thing rattles. As far as performance. I never have the money to waste to find out. All my dyno runs are w/o.

227.3 awhp on a mustang dyno
248.9 awhp on a dyno dynamics