You may have a dead rod and replacing it may cost a lot of money. It is good to put high octane into the engine even if it takes 89. this helps the engine from over working when you accelerate b/c there is more o2 in the combustion chamber.
also try checking yor spark plugs. i dought that may help, but sometimes you never know. they could be dirty and may need replacing.
My last car had a similar problem and it was due to lack of air in the system (aka a lean system). once i got a new MAF and plugs, the problem stopped.
I hope this helps...
