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...