Rod balance

A few years back I kicked a couple of rods out of my 600 ( SVO block, C head 15.2:1 injected methanol ) - I bought a couple of new ones ( through a forum vendor ) from Oliver - we tried to get as close to the same weight as we could and I had a machine shop balance them to match, along with re-balancing the rest of the rotating assy. I recently had another bearing issue and the machine shop ( different shop ) suggested I send the rods to Oliver to be checked out. I did that and Oliver said the rods checked out ok - were rebuildable - needed pin bushings and some needed re-sizing, but they checked the balance and found 4 grams difference in the rods - mostly in the big end. Oliver does not recommend taking more than 2 grams off of a rod - I know the newer ones were already a little heavier and had already some taken off them - and the older ones have a ton of runs on them, so when they offered me a deal on a new set I went for that. The most recent bearing failures were #2 and #7 rod bearings - the new rods were on #2 and #6. The rest of the bearings looked real good except for a small sort of half a football shaped shiny spot in the bottom rear of #4 main. There were some indications of a little cap walk on the mains. It wasn't real dry when I tore it down and that along with the pin bushings and cap walk had me thinking detonation might have been the cause of the bearing failures again. When I kicked the rods out a few years ago we attributed that wreck to detonation from having sucked the bottom out of the intake gaskets, I freshened it up about 180 runs ago and the bearings looked real good at that time - except for that shiny spot on #4 which was there then as well. I'm not sure what if any role the weight difference in the rods might have played in all of this. Just looking for a little input.
Thanks,
Kurt.

A few grams one way or the other isn't going to make any significant difference or cause those sort of problems.

An "above average" balancing person can adjust the placement of the rods in the engine ( usually more towrd the center) and compensate for the weight difference.