I have to hold the button for over 10 seconds on my '91 to get it to clear. I hold it for a 20 count to be sure.

Can you hear the TPS click as it comes off idle?

Have you ever cleaned your idle air control valve? If not, it is due. Look hard at all the air tubes for cracks when you pull it off.

Clean all the nipples where vacuum hoses plug in.

I spray carb cleaner through my mass air flow meter whenever I have it off. There was discussion lately about what cleaners might be safe. I just use whatever I have on the shelf. It has not destroyed it so far.

If you have EGR, clean the port at the intake manifold, and while you have it off, make sure the EGR is seating and not creating a vacuum leak.

Clean the flame trap and associated hoses. As the miles add up, you have to do this more and more often.

If you have not replaced your intake manifold gasket, you are due. Fuel injector O-rings are probably still OK.