I took it to Advanced Auto and he said that the connection under the drivers seat is a dealer only hook up and is obd1.The car is getting over 20 mile /gal. but their is a squeal noise every so often while driving under hood on the left side while driving. and the tranny or engine hesitates once in a while,also the engine down shifts out of overdrive if I am going up a slight incline on the x-way(never did that before)

20mpg is about it, 93 octane gas is better and use some injector cleaner and dry gas ,the one that is safe for catalytic converter ,if u have not tune up its time . get a thin piece of wire put one end in Te1 and E1 in the check connector under the seat, turn the ignition on (do not start it) the check light will blink. eg code 42 will blink 4 times then pause then blink 2 times .if there is more than one code it will continue to the next code write them down buy haynes repair manual chapter 6 emission have the meaning for each code.