W150 wont start.

Had problems starting for a year which was usually fixed by using ether and jumping it. It recently died while i was driving so i replaced the battery and alternator because they were on warranty anyway. Now i cant keep it running, it will start sometimes but when i hit the gas it backfires and dies. Anything will help. I've already changed the ecm, battery, alternator, rotor button, distributer cap, and coil. Have also tried timing the engine, but it seems that timing might still be the problem. Also i know that its getting fuel because i an see it in the carburater. I,ve also clamped the fuel line and took some spark plugs out and cranked the engine to try and unflood it. Thanks in advance.

Dodgetruckborred, what year and mileage is your truck? If you haven't fixed it yet it may possibly be the timing chain, or I've heard of a clogged cat. converter causing similar problems. Does it back-fire out the carb or exhaust?