Sluggish acceleration on 98 Ultra

[ChiAlex]

Hi Buick experts,

I now have a 98 Buick Park Ave Ultra with 59K miles. The previous owner didn't use premium gas. I started putting premium gas in it and ran three tanks of fuel with injector cleaner. Acceleration seems sluggish for this engine and I noticed that if I accelerate using cruise control - acceleration is much stronger than when I use the gas pedal. Gas mileage seems to be around 20mpg, I read that usually owners get better mileage out of these engines. The car seems to be idling fine, starts without any issues.

What do you think could be the problem for the acceleration problem? I read about possibility of throttle body or various sensors needing cleaning, but would like to be able to narrow down the possible causes.

Thank you, Alex.

 

[FFarr]

Have you had it scanned for trouble codes?
https://www.youtube.com/watch?v=b2IJGfImVvw[HERE]

 

[cg22]

Have you checked/changed your fuel filter.....it can't hurt.

 

[Goinkster]

Plugs, wires, coil packs, in that order. And, as someone had mentioned, in line fuel filter. There are ways to test the coil packs, but there are relatively inexpensive to replace. Also, check the fuel injectors. They are testable as well.