I've been trying to get the bugs out of my 88 240

it seems to idle and run not bad but if I tromp the throttle at idle it dies. Even in park
Seems like it isn't getting more gas quickly enough
any ideas what will cause this?

Its been sitting and i did the timing belt cleaned cap and plugs changed TDC sensor played with the throttle stop since it was kind of bent from trying to adjust the idle without turning the stop screw
I think o have a tune up procedure that says to check throttle switch etc

do I need a jig to read the codes? Can I make one myself ?

Thanks
phil