88 Olds running problem

I have an 88 Olds Delta 88 with approximately 175,000 actual miles. This car runs perfect at times. The engine light does not come on. The fuel pump and filter, coil pack and oxygen sensor have been replaced. The problem comes intermittently. It always starts easily but when you are driving down the road, it will suddenly start jerking and 'shuddering' like it isn't getting fuel. Sometimes it will smooth out once it shifts gears either up or down. It seems to be worse when the weather is damp and when it isn't driven regularly but it can and has done it at various times. It has done this for a long time although when we first got the car a couple of years ago it ran perfect. It is getting worse- more consistent and instead of smoothing out after a few miles it now does it sporadically throughout the entire trip. Once, as I went to pass a bus, it took a 'spell' just as I gave it gas to pass and it actually backfired and split the air filter compartment. It hasn't done that again. Any suggestions or ideas?

Just make sure your spark plug wires are not touching the engine block and rubbing it. Use a spark plug wire separator to separate each spark plug from each other and use a tie wrap to keep the spark plug wires away from the engine block.