Toyota Repair: Engine chugging at idle - more at temp than cold, throttle position sensor, vacuum hoses

Question
Have 91 cressida 6 cyl that cycles between 200 and 800 RPM at idle, much more when warm than cold. Have had computer codes 13 (though I think code very old) reset and some time later had 25. Have checked dist. cap/rotor, plugs/wires, vacuum hoses and throttle position sensor. Turning on the air raises the RPM and it nearly stops when idle reaches 950 RPM. Runs fine when driving but imediatly chuggs or dies when coming to stop especially if air not on. Any ideas ?

Answer
check the firewall on the right side. There is a 6 line rubber connection (like a little udder)to the Vac lines that dries out and cracks.

Check the coolant level. If theres air in it it can flucuate the idle. It gets a bad signal from the sender when theres air around it,

Mike