what are the actual power gains after replacing/modifying the y pipe in a 2003 super duty, a certain website claims 35 hp on the dyno which seems a bit far-fetched to me, but besides a throatier sound are performance gains significant? My exhaust guy said he could do the modification for two hundred dollars; is it a worthwhile investment?
The "somebody website" uses the same formula for figuring the K&N sticker and CAI add's 35 hp to the engine too! (grin).
Check out muffle flow test on the net- you might be alitlle surprised at the results of different mufflers. Yes, the y pipe could be better, does it help, sure, but considering the biggest flow restrictor is just down from there (the cat), how much good are you really doing? ya know what i mean.
I would go with the SPD replacement y-pipe section. SPD Performance Just cut out the bad section and weld in the new SPD piece. You will then have an all mandrel bent y-pipe thats fairly equal length. You should notice a power increase. As for the 33hp 35tq claims not on the 5.4l maybe on the 6.8l at a given point in the rpm range.
If you want more power a good tuner can help a lot even on 87 octane. (See thread)
I put the SPD Ypipe and a flowmaster FM70 on my V10 and love it. Most noticable is the tip-in performance. Muffler guy charged me $110 to install both. IMHO - good mod and worth the money. Definately read the 5star thread. I bought the tuner and it is without a doubt the best money I have spent.