I have a 2007 1500 Classic WT, Ext cab, 4X4 with the 4.8 V8
It performs great except when towing our RV. I have the tow package, the transmission and suspension handle fine, the engine just doesnt have enough power. Any suggestions for best modifications to make that dont involve a Duramax 2500 LOL.

 

there are many things you can do, cold air intake, true dual exahust, throttle body, computer reprogram kit, the list can go on, but the price goes up from there and can include a cam, supercharger and a complete computer reprogram from a professional, new rocker arms (with less deflection), or gear ratios, but with the tow packageu may already have 4.11 gears i hope this helps

 

most of the guys here start with the basic 3. computer tune from blackbear, exhaust, and cold air intake.

 

how many #'s are you towing? all thing listed above is a good start. sounds like the 5.3L would have worked a little better for ya.

 

you could get a quick shift kit, and a turbocharger.
While cruising, the turbo will actually get you better gas mileage when the turbine is not providing added power.
The turbine atomizes the air going in so there is less unburned fuel.
It is like around $3,000 but a turbo will be the only mod you need to do to get
more power and you will definitelly notice the added power too.

 

RV weighs in at just under 6K.
Wish I had gotten a 5.3 but the RV bug hit later then the truck bug LOL

 

if you are a do it urself guy. you can turbo the truck for $1000 then take it to a local tuner and have the computer done. i did my truck for about $700 but i knew some short cuts.