94 gmc sierra 305 wants to quit goin down the road and it doesn't have much power until u hive it a good amount of gas, when it wants to quit the lights flicker

Altenator? Lights should not flicker. Check the Battery voltage. Check the battery voltage with the engine running. The differance is how much your altenator is putting out. Battery should be around 12. Running you should be close to 14 or higher. Best option is to load test in both conditions, I use a 100 amp carbon pile battery tester, finds most issues. If the volts look good back to the fuel. Check the fuel pressure, if it's low check the fuel regulator (built into the back of the throttle body). It can be taken apart and check and usually cleaned and re-assembled without a new gaskets. If you have the quick connect fuel lines you may need the disconnect tools (cheap) if they're hex use line wrenches on them. Jegs has upgrade parts for the reg, rock auto has kits. It's usually just dirty thoough. Good Luck.