I went to a local truck accessories shop to price a hitch and electric brake controller. While I was there I talked to the guy about eventually doing some performance upgrades on my 07 STX 4.6L that I just got last week. I told him I wanted true duals with the tailpipes in front of the rear tires with an X-pipe. He said I'd loose too much backpressure even with a 2.5" piple. He suggested doing a 1 into 2 flowmaster and exit out the back. The gas tank would be in the way to exit out the left side and there would be too much pipe to curve around the tank. I haven't looked under there yet so I don't know what it looks like. Am I getting straight talk here and would I be better off with a 2 into 1 system? I do haul a small RV and bought the truck for a bit more power over my V6 Sport Trac.

 

He is right for the most part. A true dual system, especially a 2.5 inch on a 4.6, will just cause more harm then good in the performance department.

A SI/DO mufffler would do better, but not a Flowmaster...

 

IMO he saved you money and told you straight. With a fairly stock engine there's a good possibility you would lose mid range punch with the duals and x pipe. Probably make more hp up high in the rpm's with the X but lose the mid range torque you want for towing and normal driving.

 

What muffler would you suggest then? Magnaflow or something else? The Flowmaster he showed me was a SI/DO.

 

agred 2.5" is too big- especially on a reving 4.6=keep it 2.25" with x pipe true duals and you will be happy-the 2.25's on my 5.4 flow plenty-phil =btw- i gained tq on my setup-

 

I replied to your other posts in the OEM dept. of the site.
The 2.25" setup actually sounds pretty good for duals.