Finally got around to changing my main serp belt yesterday(at 134k lol), it was cracked pretty bad, replaced the two main pulley #2's PN 16604-0P011, the tensioner and pulley #1 was still silky smooth so left them. After reassembly, I noticed that the SC pulley frame looked a bit off and caused the lower SC roller to be offset to the back so the belt was on front side of the roller, almost over the rounded part, also the roller looked to be a millimeter closer to that lower frame mount bolt. I thought it was a bad roller so installed another one and the same thing. Had to remove all the SC frame and discovered that the new OEM 16604-0P011 has a skinnier bearing journal! This offset everything back 2-3 mm. Probably OK for a non Mag SC setup but wasn't ok for us! So all I had to do was install a washer behind the engine roller 16604-0P011 and that set it back out to where the old bearing journal had everything sitting, reinstalled the SC frame and rollers and all is perfect.
Be sure and check your new OEM rollers if you haver a Mag SC!
Pic for reference before removal
SC stuff out, now the tedious task of swapping the main serp belt, yes much easier from the bottom but didn't feel like removing my CBI skid and laying on my back
All new and ready to go. The circled area is the problem pulleys, washer was installed behind new pulley, all lined up perfect. When you assume the new OEM pulley is exectly the same, right?! Thas caused a lot of stress trying to diagnose and rip everything out again. Oh well.