Cadillac Repair: 92 Cadillac DeVille error codes, cadillac deville, throttle switch

Question
I ran the diagnostic check and got three codes: E27, E40, and E91 (yesterday I was only getting the E40 code).  The "Service Engine Soon" light is on.  The car starts intermittently, sometimes it is necessary to wait 10 minutes before trying to start it again.  The starter and oil lines were just replaced last weekend.  Engine is running very rough - doesn't accelerate very well when starting up from a stop.  If I take my foot off the accelerator, it dies, so the only way to keep the car on is to drive with 2 feet.  Is there a way to fix this myself?

Answer
E027 = Open throttle switch circuit.

E040 =  Power steering switch problem.

E091 = PRNDL problem. (similar to neutral starter safety switch).

There is ways to fix these problems but it will require several pictures and numerous diagnostic procedures. E-mail me at: onlineautohelp@msn.com