What's the rough power differences between the two? I've got flowmaster weld-ins, and I'm thinking of goin with Magnapac's because I can get my hands on a brand new one for $300, If there is a good gain from them.

 

not much. Maybe 2 hp and thats not peak hp.

 

I'm not sure exactly If weld ins give you any power, or even what they do besides give you a better sound. But when you get a cat back, the major difference is your're swapping out your stock exhaust pipes topipes that have a larger diameter. Because of the increase in pipe diameter,a cat back will scavenge out more exhaust gasses from the engine than weld in mufflers, thus giving you more power.

 

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What if I put LT's, o/r x-pipe, and flowmaster 10 series turndowns, will I lose power since I'm not using a aftermarket catback?

 

My '03 GT came to me with welded in (to the OEM pipes) Flowmaster's, they were too loud and I welded in a set of Maganflows. I also installed a UPR 2-1/2" catted X-pipe...[/align][/align]2 or 3 weeks ago I ran in to a deal on a pair of newDynoMax 2-1/2" tailpipes ($70 for the pair) and cut out the Magnaflows, made a set of 2-1/2" custom X-pipe to muffler connectors and welded the whole thing up--much better sound, and I picked up over 1 MPG to boot (which has to equal some power gain). [/align][/align]I had no idea that the OEM tailpipes (2-1/4" OD I think) were that restrictive with the 2-1/2' X-pipe![/align][/align]So, short answer = catback...[/align]

 

No, you would gain some power from the long tubes and mid pipe. But you would gain a lilttle more If you had a cat back to go with that combo.

 

it all depends on how much money your willing to burn