GM-GMC: 1993 gmc 1500, gmc 1500, sensor tps

Question
Have a 1993 gmc 1500 that runs good on take off but when push gas for more acceleration it boggs down and hesitates and loses power.  Already replaced map sensor, tps sensor, fuel filter, fuel pump, distributor cap, plugs.  When take breather off of carbutor and hold a towel over it, truck runs fine.  Can you help me?  

Answer
A few things your can check....check your ignition timing, also check your fuel pressure (even if the pump is new), and also have a look at the pattern your injectors are spraying with a flash light. They should be a nice even cone pattern, not dripping or squirting streams of fuel.
Hope this helps