We have a Vista diesel (last one built in 68) that we use often for heavy PTO work etc. The exhaust doesn't sound clear or crisp like those engines should. Sort of sputters or flutters as the RPMs get over 1200 or so. At high idle it's not smooth sounding at all. A little history, we've owned it a long time. It sat for a few years because the back seal leaked too badly to use it for anything and it almost stuck from sitting, I suppose from condensation in the cylinders but a few years back I overhauled it. Had the heads completely worked over, new valves and seats and I honed the cylinders down and put new rings on the 30,000 over pistons that we had installed when it had been bored years ago. I had to have the pump worked on to replace that plastic retainer that goes bad when they sit. I didn't do anything to the injectors then. It fired right up and sounded pretty good too but lately it's getting worse sounding. I just pulled the injectors out and took them to Midland Diesel in Fargo and they rebuilt them. Installed them today and no change. Pulled valve covers off to check valve lash, none were tight, a few a little loose so adjusted them and all that did was make a little less tappet noise but still sputters. Could the pump be doing this? There Is next to no blow by, you can pull the dipstick and nothing comes out while running. I suppose I need to make sure by checking compression but not sure how to do that on these type of injectors. How about the energy cells, can they cause these problems? I know it's nearly impossible to remove some after years and years of use. Any ideas would be surely appreciated. Thanks.