Captain, I need more power!

Hi all,
I just returned from an epic voyage of 2550 miles in 46 hours from Vermont to Missouri and back. First real trip in my 02 Silverado. Trip there went great, picked up a load of trailers weighing about 7000 pounds, (1 car hauler and 4 utility trailers on top) and headed back. I havent checked the mileage yet but it was about 1/2 what we got on the trip out. The real issue is power. I have the 4.8 engine, the transmission would keep downshifting into a really low gear, second I suppose, bringing the revs up to about 4000. To get it to shift out of that, I had to take my foot just about off the pedal, loosing speed, and then it would want to downshift again. I feel like if the engine had some more giblets, the transmision would not need to be downshifting as much. The truck is fine as it is for 95% of my use, so I am not going to go out and buy a 2500HD for this. What engine mods are going to give me the best bang for the buck? A new chip seems to be in order. Are there different ones? How about a throttle body spacer? What will I benefit from that? K@N air filters seem popular also. What sort of horsepower gain would those 3 improvements yield? I think flowmaster exhaust is outside the budget at this point. I am pulling my 57 Dodge Power-Wagon from Vermont to Iowa for a rally in June and this will want to be ironed out for that.
Thanks in advance for your help, Tim

Hi all,
I just returned from an epic voyage of 2550 miles in 46 hours from Vermont to Missouri and back. First real trip in my 02 Silverado. Trip there went great, picked up a load of trailers weighing about 7000 pounds, (1 car hauler and 4 utility trailers on top) and headed back. I havent checked the mileage yet but it was about 1/2 what we got on the trip out. The real issue is power. I have the 4.8 engine, the transmission would keep downshifting into a really low gear, second I suppose, bringing the revs up to about 4000. To get it to shift out of that, I had to take my foot just about off the pedal, loosing speed, and then it would want to downshift again. I feel like if the engine had some more giblets, the transmision would not need to be downshifting as much. The truck is fine as it is for 95% of my use, so I am not going to go out and buy a 2500HD for this. What engine mods are going to give me the best bang for the buck? A new chip seems to be in order. Are there different ones? How about a throttle body spacer? What will I benefit from that? K@N air filters seem popular also. What sort of horsepower gain would those 3 improvements yield? I think flowmaster exhaust is outside the budget at this point. I am pulling my 57 Dodge Power-Wagon from Vermont to Iowa for a rally in June and this will want to be ironed out for that.
Thanks in advance for your help, Tim

A programmer is one of the best mods for the money. There are several choices(Superchips, hypertech, Predator, Jet performance) All of these do about the same thing, so unless you get a custom tune, just shop around and find the best price on one. Only get a throttle body spacer if its given to you(like mine was). It helped me out alittle, but I don't think I could justify someone paying $100 on one. It would be better to get a whole new intake system. The k&n drop in filter does alot better than the stock filter, but you will notice alot more performance out of an entire intake. An exhaust system will help out a great deal, and you can get a catback pretty cheap if you look around. I gained a great deal of power from my mods listed. I also have the 4.8L. I gained almost a full second on my quarter mile time, so I'm sure it will help towing out a great deal.

I recently put a K&N in my 94 and i have been really impressed with the added HP for 40 bucks it couldnt hurt

Just to get one posibility out of the way, you had it in Drive, and not Over-Drive. Correct?