when I got my 2.6 rebuilt 2 years ago in my 88 D-50 I had the BSE kit installed and my engine rebuilder told me he had done tons of these and never needed balancing. So when I started driving it the vibrations were so bad that it rattled 2 of my oil pan bolts loose. And at Idle my signal/wiper switches would rattle and made noises, the change in my ashtray would rattle. it was hell. so when that engine died 4000km later (not BSE related) I had him balance it on my warranty rebuild. he had installed 1983-86 pistons with 87-89 rings. you wouldn't think it would make a difference but it broke every piston ring into pieces.