im planning on putting a 4in exhaust on. will i have to get a bigger down pipe or will the stock one work?

 

If you get a turbo back system the DP will be part of the kit. Seems useless to make the cat back 4" since the OEM tubing is already 3.5".

 

this is the one im looking at but i dont see that it comes with one.

MBRP S6212SLM 4in Turbo Back w/ no Muffler in 409 Stainless fits 03-07 6.0L Ford

 

Top two pieces are the downpipe.

 

Ok cool. Thank you

 

My 2003 had a 3" down pipe to the resonator, then 3.5 to the cat, found that out the hard way. OP, measure your down pipe, being an early 2003, my 3" down pipe could have been phased out for a 3.5" piece on later trucks.

If you have the means to support the trans/x-fer case, I'd drop the cross member when stuffing the down tube/pipe. This would allow for marking and welding that 2-piece pipe. Otherwise, you need small ands and lots of patients to properly tighten that clamp.

Make sure you clear the cross member when your done, when mine ratttled off of the cross member, it made me homicidal.