Rough Ride

[wolfsburg78]

I have an 89 Electra Park Avenue with 230,000 miles. I got the car after my mother in law passed away in October. I recently replaced the EGR valve, coil, fuel pressure regulator, PCV valve, intake manifold gasket and added seafoam to the gas tank. The plugs and wires were replaced about two years ago along with the fuel filter. It will run fine most of the time but sometimes will suddenly start to run very rough and shake hard if I try to give it more gas and will idle rough after this. It will do this at any speed with no warning. I do notice the RPM’s drop just before it starts to shake as if the transmission has shifted gears. It also seems to run fast; that is it will almost maintain speed without even touching the gas. I have to keep my foot on the brake going up my street to keep from going too fast. Any help would be appreciated.

[Scrapper]

i would think it would be a plug or spark plugs and wires. a plug or wires would do that when giving it gas. under the power your trying to get up to.