John Deere 110 TLB engine lugs when accelerating

[JD110TLBFan]

I have two late model John Deere 110 TLBs where the serial numbers are in the after range of (311032 - ), e.g. starting with digit T4 or higher, so there is no Engine Speed Sensor (LVA11184). The symptom I am experiencing with both is that accelerating from a stopped position to full speed (say at 2000 rpm) in B range noticeably lugs the engine, as does going up a slight slope in C range. It sounds like the engine is about to die. If I let off a bit on the accelerator, the engine recovers. And once full speed is achieved, the engine recovers. I do not detect any surging symptom, and the tractor doesn't stop (like when your butt comes off the seat sensor), and there is no fan belt squealing. Engine oil and transmission oil both are within acceptable level and very clear (was serviced recently, but this problem predates the recent service). Both the inner and outer air filters are branch new. The fuel shot valve is in the "ON" position. One had both its fuel filters changed and that didn't solve the issue.

This doesn't happen with my early model 110 TLB which has the engine speed sensor and presumably compensates for the added engine load with more fuel or something. On that early model, I can accelerate from stop to full speed without the engine sounding like it is about to die. One time I disconnected the early model's engine speed sensor (on the flywheel housing) and it behaved a bit like my late model is currently behaving where load causes lugging. So I know what the late model "should" sound like it it were operating properly. I bought the late models used so I don't know what it was like when new.

Given that the late models have no speed sensor, I did some searching online and I see others mention that Deere replaced discontinued the speed sensor replacing it with something to do with the alternator.

So I have two questions for late model 110 TLB owners:

1. Has anyone with a late model 110 TLB experienced this engine lugging symptom and/or fixed it? Did it have to do with the alternator?
2. Can anyone with a late model 110 TLB confirm that they can set the RPM to 2000 and accelerate from stop to full speed in B range without the engine lugging (some minor reduction in RPM might be expected, but this is more than that)?