I'm not sure what is going on I just purchased truck it was running fine a decided to put hot shot fuel additive in and a day later truck ideals fine starts fast but under load shakes and runs rough but not all the time. The service light never comes on.

 

 

Sorry, fuel tank is half full the guy I bought it from said the fuel pump hab been changed, the pickup in tank was changed, but I didn't see receipts also the cam shaft sensor was changed.

 

 

I'm not sure I will check it out it start fast even cold so I wasn't sure if that was it.

 

Could be the fuel pressure regulator. They seem to have trouble along with fuel pump problems.