I am getting very sluggish throttle from my 2011 fx4. I know I won't have the power like normal due to my lift and 35s. I was wondering if it was due to my air flow. I have an afe intake and my pipes coming out are 4.75" to a flow thru muffler. Do I not have enough back pressure? What can I do to fix or minimize this?

 

Between your muffler and factory cats, back pressure isn't an issue. How many miles are on the truck? What gear ratio, what motor, and have you had it tuned?

 

Back pressure is more an issue than some realize, 4.75" pipe? Ever have chest congestion and try to cough and get no relief but block your mouth and get flem out? Same principle.

Get the pipes back to no more than 3", put a turbo muffler or at the very least a cherry bomb (glass pack) and buy a tuner. Problem solved.


EDIT: If you have a 6 cylinder either n/a or turbo, my answer may not be accurate, I base my statement on v8's.

 

I have the 5.0. I will have to try to get the pipes brought down. Most of the work was done before I got the truck, so I kind of thought this would be the case.

 

64000 mild are on it and I have the 5.0, hasn't been tuned to my knowledge. Gears are stock as far as I know. Most of the work was done before I got the vehicle.

 

It could be the gears. Check the drivers door jam
It will have a letter/number classification.

 

I see axle L6. Is that what you were referring to?

 

Yes. That is it. L6 is a locking 3.73 gear ratio. Should be more than enough to move those tires.

 

Sorry it took so long to update, I just got back front Europe with the army. So I got the pipes dropped down to factory. I put a new muffler with 45° turn downs just before the rear axle. It didn't do much for the lag, but did improve my low end power. I will be getting a tuner next month and we'll see if that helps at all. Thanks for the help guys. If y'all think of anything else, please reply.