Some of the other culprits in a DTC 61 are bad actuators, 2* solenoid, leak anywhere in the vacuum hose spyder for the 2* system, and a bad ECM.
If the code 61 sets the motor will be limited to 3k rpm. It's like driving a toyota!
I had this on my 90 about a month ago....turned out I pulled the plenum for nothing as it was the ECM. If you have a spare swap it out & see what happens. It might save you a plenum pull.
Tom