I really appreciate all that feedback-it is very helpful as i think things through. I am hoping i dont have an injector pump issue as funds are tight right now but all of us just want to troubleshoot and get to the truth.
Went out last week and took the bypass line off and checked the fitting coming off the injector pump-it didnt have a little ball in there, just open fitting and i checked it thoroughly-had no dirt or obstruction - blew it out and blew the bypass line out again. The only other thing i noted was that my brother in law had run most of the fuel out bushhogging. I like to keep it full to cut down on condensation, etc, so i put 10 gallons in which brought it a bit over half full. I then went out and bushhogged for a good 45 min to an hour--a good heavy load - ran perfectly. Brother in law then 2 days later was bushhogging again and the power issue came back again, ran erratically and now i will go back Saturday and see what i can discern.
After this final issue, my thought is that there is debris or sludge in the tank bottom that is interfering with the outlet line. I am wondering if, when i put 10 gallons in it stirred up whatever trash was at the bottom and it ran fine. Then after 2 days, it all settled to the bottom again. Since it ran perfectly for me for almost an hour under heavy load, i am hopeful that this is not an injector pump issue but trash in the bottom of the tank.
If anyone has any final thoughts-i would love to hear!