Hi Gary,
Jez I'm sorry that the signal went belly up! Yes I have that tune and thus far it is the best money that I have spent on any performance part for my car.....actually it's the only performance part my car has!
Everything that you are describing is typical of the 1990 EPROM with the AUAH programing which GM replaced with the AYBK program in a TSB as an answer to the complaints from owners. It was a big improvement over the AUAH EPROM.
I should say that I'm even more satisfied as I bought an AYBK EPROM from GM when they were still in stock and it corrected the idling issues and the coast down issues, but Marc's tweeks to the AUAH programing include eariler fan "on" temps to yield an operating temp closer to 200*F vs the GM 220*F programing. Marc also cleans up the fuel map so it is more effective at part & cruise throttle settings. Overall it's the best money I've spent on the car besides tires & gas! I highly advise any 90 owner to get Marc's chip!
Tom