I reported a long time ago that I was having issues with speed matching on my last two consecutive brand new MTH G scale Dash 8 engines only. I got a PS2 and later a PS3 dash 8s that ran too fast. When I contacted MTH about it, they figured I didn't know what I was doing and probably was trying to match them with some non standard upgrade. I actually had another engine doing the same. It was bought used, so I didn't count that one.
To the point, the engines are now fixed. The latest PS3, I had to fix with a dremel. MTH doesn't offer any tach reader with shims for PS3 I guess? I used a medium shimmed one to fix the PS2 engine.
I had to get the PS3 tach reader closer to the flywheel which is difficult on their G scale. The spacing is fixed by the plastic housings. So I grinded that space down and got the reader much closer. It seems to me that the PS3's reader's head, is much smaller and would need a shim on any older application that was setup for PS2? Again, I'm the only one who reported this so far. So if anyone out there needs a fix for speed that's too fast, it maybe the reader's spacing. Maybe no one else uses them in consists? I can now use mine in any consist I build.