I have a 1993 bonneville ssei recently baught , and i was expecting some decent to good acceleration out of it , but when i give it a hard shot of gas it accelerates horribley , I have an accelerometer and it took 11.49 seconds on a 0-60 run . when i expected mid to high 7 second 0-60 . under respectfull acceleration it handles fine, do you know what the problem could be , the old owner used blend gas the 89 octane the middle priced gas ,

Your engine (supercharged) has a high compression ratio, therefore its important to run premium fuel. Thats one part of your problem.

The other part is that the car is probably due for a thorough tune-up, including cleaning the throttle body. Once you get those things taken care of the car should definitely wake up.

Your car REQUIRES premium fuel of 91 octane MINIMUM.

Your car does NOT have a high COMPRESSION ratio, but does have high EFFECTIVE compression when the boost pressures are factored in. You are slowly destroying your motor over time by running sub-91 octane.

When was your last full tuneup? Including plugs and wires? How old is the O2 sensor? How long ago was the TB cleaned?

i think he said the previous owner ran the low-mid grade fuel, not that he was running it.

We'll need clarification on that considering the way it was written.

And if that'* true, plugs are shot for sure. I'd be curious to see what the plug gaps have eroded to.