The BS's have nothing to do with rotating engine balance in the usual sense. I4's have an inherent second order shaking force no matter how they are balanced. This force causes the engine to rock fore and aft, and is caused by the slight offset of the piston pin in the piston which reduces the piston wall-piston friction on the power stroke, and makes the piston accel and decel at different rates on the upstroke and downstroke, this imparting differing forces on the block. The upper limit for an I4 is about 2000cc's without the shafts before you get unacceptable shaking. You can balance the rotating/reciprocating parts to within a millionth of a gram, and it will still shake.

My horror stories on bse's. I had to weld up the ps pump bracket a bunch of times when it fractured due to the vibration. This happened both n/a and turbo. My a/c compressor bracket turned into metal gravel, and since it was pot metal, I had to swap compressors and brackets to the cast iron version. I finally put the bs's back in, and no further problems. The rv mirror is so buzzy at cruise, you couldn't tell if there was something behind you or not unless you put a hand on it to damp the vibe.

Unless there is damage to the bearings, I hardly ever changed them out. I just put on a new chain and sprockets and guides and called it good. I never had a bs bearing failure. I do like a lot of oil pressure, and used to shim the oil pressure relief valve spring with a flat washer to increase the tension, and thus the oil pressure. It's under the big hex nut at the top of the oil pump, pointing to the dside. Others scoff at this mod, but I've done it for years, and it's good for 10-15pai of hot oil pressure.

I realize I'm in the minority in this opinion, but there's a damn good reason for the shafts, and while I may be wrong, I'm still certain I'm not. Porsche thought enough of the technology to pay Mitsu royalties to use it on the 924-944, and Porsche engineers are not stupid...