Hi yes when this engine was new you would have had 300bhp. however over time and there has been now some 13 years of time and miles that has been now been reduced to about 30 bhp.

yes overt time and wear in the engine it has all gone.

so what is the answer either a new car or a new engine.

Throttle body spacer is a waste of money. You have no carb to swap.

Dual exhausts with X tube

biggest limitation right now is the cam.

I have a stock 2000 chevy silverado 1500 5.3L...all i have in performance upgrades are a bullydog gt tuner and everything else is stock. Ive done some research and have found im getting probably around 300hp right now...im looking to get a lot higher. Idk if throttle body spacers, exhaust, carb swaps. Idk what would be the most effecient and cheapest ways to take to get my truck some horsepower and would like some opinions. Thank you