I got my car dynoed at the rear wheels once with the cutout closed through 2055's and hooker cat-back, then with it open just after the 2055's. I gained 7 hp all above 4000 rpm. Surprisingly the low end did not loose any torque or hp. Torque jumped too above 4000 and even at 2500. My car pulls one tenth faster with he cutout open at the track, but runs a little more sluggish way down low on the street. I was running a little rich through the muffler and I thought that the cutout would have made the A/F near perfect, but it actually got richer when I opened up the cutout. Maybe it is because it is sucking more in and out with less backpressure.

 

Thanks for the info. I love getting on this website and finding info that directly answers a question of mine. I am going to buy those same headers but I have been on the fence about keeping the mufflex 3.5 inch catback that I bought or just get a 3inch catback. I cant imagine the mufflex will flow better than a cutout so for a tenth or two I will save my money and sell the catback.
Thanks again.

 

Remind me where in the system you installed the cut-out.