Just wanted to thank you all very much for input and sharing, don't want to be ungrateful. I had some success with 120 E acceleration and 0.03 PA. On a side not my prints look a little different since moving from direct to nimble, walls have weird "pattern". I need to test more to eliminate speed factor. Also ill be looking to get that portescap stepper it seems to be a way to go. Again Thank You!

Update: Just found out that actually pressure advance is the cause of slowdown. so can I keep PA with nimble?

Im fairly new user of RRF but Im a convert already! Anyhow my problem is that Zesty in their documentation is saying "M566 should have E value set to E40 (as it is set per minute)" but if I do that my printer(corexy) would really slow down acceleration seems to be maybe 500 or less by eye even though its set at 2000 in firmware. As soon as I increase M566 E40 to lets say 80, its speeds up. Obviously i dont understand relations between print acceleration and E jerk. What am I missing here, leaving it at recommended E40 is not an option as is.