Will installing one of the mentioned axle back's make your car lose power/torque?

I've done many exhaust upgrades to the 99-04 GT's and when I installed magnapacks on one of them, I lost quite a bit of power.

How would it be for a 07 GT500 Shelby?

 

I highly doubt it.

 

Should be gaining power by taking off restricting mufflers.

 

I remember when i got my muffler delete i could feel the pressure building up and it did feel a little slower. I would deff go with a brand name rather than getting a muffler delete.

 

Sham wow!