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I have a 1993 Buick Skylark with a 3.3 liter engine. It shudders and "pops" when under acceleration. Especially hard acceleration and uphill. Runs ok around town though. Fuel filter has been changed. Will get better-sometimes- if you let off the gas. Looks like the tps and idle air control valve were replaced by previous owner. Also does this when running on interstate around 70-80 mph.  

1993,eh?

Wait until it's night and rev up the motor while looking under the hood and see if the sparkplug wires are arcing.

Remember to lock the emergency brake and block the tires befre you do this.

You can also check the spark plug wires to see if one is burnt.

This car must have alot of miles on it.

The motor could have burnt valves-expensive.

There could be a minor electrical problem.

There could be a major electrical problem.

The fuel pump could be bad.

The fact that other parts have been freshly replaced means the person you bought this from may have been chasing the problem before you-got some bad info and got rid of the car.

If you have someoene you can take it too and get the car's electrical/motor system 'coded',you may get an answer to what the problem really is.

Otherwise,you might spend a fortune replacing parts on a car you need to sell for parts right now.

Simple things could be wrong too, though.

An intake gasket leaking-an air filter that is simply plugged it's so filthy.

Even a loose wire somewhere under the hood.  

chances are its your fuel injectors.id have them checked.or at least have them cleaned .  

Ther is a great idea for you to use power exreactor engine. To double the power output of your present vehicle, you could add a second engine equal to the one you already have.