After fiddling w a MyECU P8 a year now,
this feature do suck. Period.

In short,
to alter TPS at idle or other TPS alterations, DO use Wordpad or similar.
EcuControl can only handle one change, then its crappity showes up, viewing wrong values, numbers on side of the tic-tac-toe pattern in opening window are doubled (=ureadable...), does not altered Idle TPS etc.  :( ;)

So,
I only use EcuControl f minor or broad changes in Spk or Inj maps, period.
Prime changes do work btw.

I still like MyECU, just frustrated after trying to refine starting & idle tonight.  >:( ;)
I wish this would work better, simply...

The axis repaint is ugly thats true. A quick workaround is it minimise the window then restore.

Are you talking about the idle TPS setting or the throttle breakpoints?

The idle setting should be set early when you get the MyECU and before you start to optimise the rest of the map.
Further services may require minor TPS adjustment but not enough to affect the rest of the map.