i just did the head\valve job cuz the compression was a bit off in a few cylinders. had to do the values and shave the head flat for a .016" warp. cyl. got it running and #2 was dead. rechecked compression and all where within 2# of 165 psi. so started pocking around with the carb cleaner for a leaking intake manifold or something. leaned on the tube to the injector and it smoothed out. took oil to the seals around the little critter and it smoothed right out. so i pulled the injectors and found the Oring was as hard as rock and the insulator as well. i took all of them out and oiled them up good and put them back in and it ran great. so try an oil can to the black insulators and see if it doesn't smooth things out. new insulators and Orings are about $35-$40 and a lot cheeper than a tech's time so give it a try. good luck. jim