04 f150 4.6 lost performance, magnaflow

[rudy268]

I have an 04 f150 with a 4.6 supercrew 4 x 4 with an airraid throttle body spacer. I bought the predator u7151. I had installed the 87 octane setting and noticed an increase in torque on the start and a slight increase in mileage and great acceleration when passing. Recently, I installed a magnaflow muffler on an otherwise stock exhaust My gas mileage dropped dramatically as if the tank leaked and I can't spin the tires anymore on takeoff and the truck is sluggish.. Any suggestions to get power and gas mileage back? Thanx John

[jj]

did u ever get an answer from anyone?? i have a 2004 f150 5.4 with the same issue,, i run the 93 octane and it seems very sluggish..... let me know plz

[kmac1]

I replied in one of your other posts on this I believe...

Kevin@Diablo

[shawnobrien]

I have the same issue with my 05 F150 STX with JBA headers, Spectre CAI, and Magnaflow catback. Did you guys find out anything? I could sure use some help tuning mine in. Thanks

[Mike_Levy]

The problem is that you now have zero exhaust velocity. You need velocity to make torque. You freed up the exhaust side too much and didn't do nearly enough on the intake side to compensate.