95 GA Compute Problem ?

1995 Grand Am GT, V6 with 240,000 Km. Engine light comes on when driving on the highway and won't go off until engine is turned off. Oil light comes on some times when driving. It goes off sometimes and on other occasions will stay on until engine is turned off. I had both of these problems checked out at the dealer. They told me that it is just a bad sensor and nothing to worry about, just keep checking the oil to make sure it is not low. Well, the other problem that is just happening now is that at times when I start the car, either first thing in the morning or during the day, the engine is revving at over 2,500 rpm and no matter how long I wait, the idling does not go down. You can imagine the beating the transmission is taking because I end up just putting it in gear. This is also a problem when driving because the car will do 40 to 50 km per hour without even touching the accelerator. When the brakes are applied, it is also very hard to stop the car. The other issue that is happening now, is that the oil pressure gauge will at times go all the way to the right (500) which indicates extremely high oil pressure. I took it to the GM dealer and they told me that everything is pointing to the engine computer. Before I go ahead and get this replaced I would like some input from someone that knows about these problems. Are all these problems related ? If it is the computer, can it be reprogrammed ? Is this a common problems with GA s ? Thanks.

The computer is a possibility but before changing it try looking for a vacuum leak. This can be due to lower intake manifold gaskets leaking and allowing more air than usual into the engine or it could be a cracked vacuum line. As for the oil pressure change the sending unit. Should be located above the oil filter and isn't hard to change. These go bad and will cause the issues you describe. If you can't find anything wrong try a computer from a wrecking yard. They are much cheaper than a new one and they are not hard to change. I would also change plugs and wires if you haven't done so recently as they could be causing intemittant misfires that is causing the CEL to come on while driving.