95 computer ?

I have a 95 chevy silverado 4wd with the 350. Over the weekend, I had a problem and when taken into a shop turned out to be the timing had rotated somehow. It had retarded 17 degrees. Dont ask me how because i cant tell you and neither can my mechanic. He told me to drive it for a few days and bring it back if it needs it. It seems to me that the computer is having a little trouble adjusting to the timing. It idles good, but now it revs real high before shifting, like almost to the redline, about 3500 rpms. There seems to be a lack of power in certain rpm ranges, but right around 2500 rpms it feels like it should. It is slow getting up to speed and when i was on the highway yesturday I was going about 75-80 mph and the trans shifted down and was running a little over 3000rpms. The distributer, coil, plugs & wires and stuff have been replaced recently along with fuel, oil, and air filter and fluid. I checked the trans oil and it was full. You think it is the computer and is there anything I can do quick to fix it because i cant take it in until friday. Also, on the highway, it sometimes pulses and when driving the engine sometimes feels slow and sluggish, then suddenly will kick in. Any ideas? Thanks

I had the throttle position sensor fail. It can cause all of the symptoms you have discribed.