So my 07 4.6 2wd xl has no tach. I'm trying to decide on leaving the stock muffler for torque or switching for more hp. The cats are being replaced on Monday and I have a tuner on the way as well. I tow a 4000 lb camper and I need to make as much difference at expressway speeds as possible. The freer muffler will provide more in the mid and upper but I don't know where that line is. Help! I have a home cai mod w/k&n and everything else stock.

 

I believe it's a 373 rear end as well

 

Yer kinda putting the horse before the cart here. You don't need the trick exhaust or the tuner so much as you need a tach. You can get a Scangauge or an UltraGauge that will give you tons of information you need while towing. It hooks into the OBD port at the steering column. It will give you a variety of screens to setup. I use the tach/ system voltage/ engine core temp/ and instant fuel mileage. You can program any of them to give you the exact amount of power you are making and a host of others that are available. Once you have it installed and programmed, now you have exact information on your truck which nobody here knows if it is a supercrew, regular cab, what size tires,etc. These gauges will give you the exact info. Here's a short vid on the Ultragauge and how it works. You can put it anywhere you can see it. Ultragauge costs 79 bucks. Scangauge is more money.
https://www.youtube.com/watch?v=Mo9naImUBmE

 

I'll check it out, thanks for the reply