2000 4.3 jimmy

i bought one of these about 3 years ago. as far as perfomance mods, all i have done is remove the front snorkel from the air box and seal the box to the wall with foam rubber so hot air does not get in. i also at the same time "ported" the webbing in the headlight assembly on the drivers side so more air could access the air box area. then i installed a hi-flow throttle plate, which i found out later is the same as removing the baffle from the stock plate. that's it, period. i am very mechanical, but bolt on parts for this are few and far between other than a cold air intake system. i am a computer illiterate. i am lucky to be able to figure out how to post here. so reprogramming via computer tuner things may not be the best move for me, unless it is something you just plug in and go. i thought about a freer flowing muffler, but i am a bit concerned that i might end up making my performance worse. i had a ford aerostar that dropped its muffler once, and it did not gain any power, and lost a lot of fuel mileage. what else can i reasonably do for not a lot of dollars?