Gmorning fellow wrenches, I have a 95 S-10 with the 4.3 TBI "balance shaft" V-6, 5 speed and have been strugling with a demon knock in theengine that just wont go away. Here is the history...got the truck cheap with engine noise with the intention of doing a V-8 TBI swap, got anxious and yanked the engine and set aside and started collecting V-8 parts needed to do the job, as time went by and as girl friends came and gone it was 3 years before I got back to it and fuel prices shot up. Decided to just stuff the V-6 back in it freshened up of course, noticed this engine was replaced or rebuilt at some point with machine shop stamps on the rods and crank R.010-M.010 and pistons @.030. I had the heads redone, new oil pump and timing set, I pulled main caps on lower assembly and plastigauged them and are still in spec. all bearings are good! Didnt pull the pistons but didnt see any sign of cylinder scoring still had great cross hatching and little if any ridge up top and did a quick check for skirt play through out the stroke range on all cylinders and couldnt feel any noticable side play and the wrist pins looked good. Reassembled and installed with new clutch, filters, and hoses and all gaskets of course and repaired or replaced vacum lines as need. Went through the throttle body and cleaned up, installed new temp, oil, map and knock sensors. Fired up and set timing to 0 degrees with the ecm control wire unhooked from dist as per manual. Drove like a dream for a couple days back and forth to work on the highway and what not in town monitoring all vitals and all checks great with no noises, decided I needed to take on a long range test drive for about 100 miles before taking it on vacation and all went well untill I got back into town at the toll both, the same knocking noise came back, under load, accelerating or with the A/C on and the knock sensor is picking this up making the timing go bat shit just as did when I got the truck. I did notice upon freshening this motor up that the timing chain was realy stretched considering the amount of miles it was showing on the engine inside as far as ware and tare. I pulled the timing cover and bingo the chain was stretched again. I installed yet another new premium timing chain set as per instuctions with the balance shaft marks where they need to be per the manual and no the newly stetched chain did not jump teeth, fired up noise still there. Hooked up scanner/engine monitor no codes or check engine light and temps, oil pressure and air fuel ratios and fuel pressure are where they need to be as far as factory specs. Im at a total loss/mind f*ck on what it could be not to mention the cash layout, yikes I should have stuffed the small block in it and been money ahead! Any ideas before I shoot it?