Well, Stig, it still looks like you are hot on the trail! I know reset has been discussed several times on this and other problems. I have not replaced TPS, ISC, ABV or CBS on my DT300i but the reset aka INITIALIZE fixes wonky idle. Come to think about it, reset worked on the Yager, too. However, if there is a transient problem with the TPS, reset won't be permanent. You have figured this all out.
Should NOT need the tool for a reset. BUT considering all the vagaries and errors in both the Owner's Manual, Service Manual I would not be surprised if there was a difference in how the ECU performs after the two flavors of reset/initialize.
B&L, I will be willing to bet that you and Zombie are the only two in the business that actually do a proper PDI on a new machine or one you have repaired. Therefore, do not take personally my jabs at dealers and their techs since it apparently does not apply to either you or the Zomb.
Go, Stig. GO!
Karl