Hi Karl, this is Aron GadgetmanNebraska. What you have there is a composite throttle body. Not a metal one.
These can be done, but you will need to build up on opposite side of where you are going to cut groove.
When cutting these I would us the medium size bit first.
These will melt when cutting the groove. My experience has been to turn your dremel down to about half speed.
Cut very slowly with very little pressure applied.
Watch very carefully when getting down to base of shaft because even the shaft will cut a groove.
It is possible to do these, but just take your time with them.
Nice thing I see is the iac is seperate.
Good luck. You can find awesome pictures of these on ebay motors.
Just type in the make , model and engine liters and you will see many views of these.
GadgetmanNebraska Aron Cheeek