There is some serious power loss when I have the truck timed at about 7 degrees before TDC. It sounds great and idels fine but I can barely make it up the hill next to my house in first gear. When it is not timed properly (like approximately 25 degrees before TDC) it has lots of power, but you can hear it missing (popping from the exaust). The engine is a recent rebuild that was never timed correctly to begin with. ANY THOUGHTS OR IDEAS?