Toyota Repair: Toyota bucking, toyota corolla, short circuits

Question
I hope you can help me.  I've had this problem for 2 years.  I have a 94 Toyota Corolla with a manual transmission.  About 2 years ago it was bucking while in gear.  Back then it had about 80,000 miles on it.  Right now I have 103,000 miles on my car.  It doesn't matter what gear I'm in but it does seem worse in the lower gears.  It doesn't buck while I'm shifting.  It seems to happen when I take my foot off the gas and then press on the gas to maintain a certain speed.  If I'm not accelerating it will buck. My mechanic thought I'd gotten some bad gas so we treated it with gas cleaner.  When that didn't seem to solve the problem we gave it a tune up.  That seems to solve the problem but only for a limited time as I have to get a tune up often to get it to stop bucking.  It would also stall out while I'm in neutral coasting along or stopped at a light.  It always starts back up right away but it will stall out while I'm going along at 50 miles per hour which scares me when that happens.  It also doesn't matter what the weather is or whether the car is warmed up or not.  It will happen at any time and doesn't matter how long I've been driving the car.  I'm not sure what steps to take from here whether I need to replace the clutch or timing belt.  No one seems to know why it does this.  Is this a common problem for this make and model?  Please help!  Thank you Ted, I appreciate your time.

Answer
There have been some problems in the past with distributors and coils on these engines, have the mechanic check the distributor cap and rotor and the coil which is mounted inside the distributor, they can develop cracks or short circuits to ground, the coil should be inspected very closely for any cracks or burned areas, as a last resort it may be necessary to replace the distributor if no other cause can be located.