Bought a used 2019 Uforce 800 about a month ago (only 30 hours).  Love the machine, but was kind of annoyed by the hesitation/jerky starts from initial throttle. Found this thread while researching the issue, ordered the Z800 ECU #0800-174000-2000 and installed it today.  I'm a little on the fence with it.  Seems to have smoothed out some of the issues at initial throttle, but not sure it was worth the $375 price tag.  Just wanted to let others know about my experience and it may or may not make a world of difference. 

Did you order 0800-174000-2000 or 0800-174001-2000? The first one is what I HAD in mine 2nd one what I replaced it with

I've not seen part number 0800-174001-2000.  The one they told me about at the local store was the same one others have listed here and what I've seen online, 0800-174000-2000, for the Z800 

The original ECU in my 2019 UForce 800 is 0800-174000-10001.

[2015 Z Force 800 53/Trail EPS]

It may be that not all your issues were ECU-related. May have one of those thousands of bad idle air control valves and/or TPS....and if yours has peddle-by-wire...lots of those came from the factory bad.

Bought a used 2019 Uforce 800 about a month ago (only 30 hours).  Love the machine, but was kind of annoyed by the hesitation/jerky starts from initial throttle. Found this thread while researching the issue, ordered the Z800 ECU #0800-174000-2000 and installed it today.  I'm a little on the fence with it.  Seems to have smoothed out some of the issues at initial throttle, but not sure it was worth the $375 price tag.  Just wanted to let others know about my experience and it may or may not make a world of difference. 

Did you order 0800-174000-2000 or 0800-174001-2000? The first one is what I HAD in mine 2nd one what I replaced it with

I've not seen part number 0800-174001-2000.  The one they told me about at the local store was the same one others have listed here and what I've seen online, 0800-174000-2000, for the Z800 

The original ECU in my 2019 UForce 800 is 0800-174000-10001.

My apologies. I had it backwards. 174001 was stock unit.