Okay this is an extreme newbie post here. I have the old 4.3 with 165 horse/235torque. It has 160000 on her and still runs good I think. In everyday driving I'm not totally dissatisfied, theres plenty of power for highway merging and it's quiet and comfortable doing 75, 80. However I use this truck for work (construction-I added a leaf in the back..7FT bed) and for roaming around the hills of wisconsin with kayaks on top, bikes in the hitch rack, and a bed full of camping gear. It is at these times when she feels like shes straining. I got 15.4 mpgover 200 miles with this setup and was constantly shifting down and sticking my foot in it to maintain, but I know she's capable of more.
Now this is a high mileage engine, and I am not drag racing anyone, but I know that it's about time for a tuneup AND I might have detected just the slightest leak coming from the Y pipe, so it's time to consider what sort of help I can give her. I'm thinking in the lower end of the 1000-2000$ range. I am just a regular guy who turns wrenches on his truck when he can, and takes it to the shop when it's prudent to do so. I do like to stick my foot in it occasionaly to make a move and I just want to know it's there for me a bit.
I'm interested in what real world guys out there have done to get the most bang for the buck really just to help their similar engine/vehicle breath better.

Any advice is appreciated/considered.

Thanks, Shawn