Octane Question dealing with performance...

[MaraSport]

I got a cat-back exaust system without doing anything to the intake part... After a few days to a couple of weeks I felt like the car was sluggisher than it was with my stock single outlet exhaust... So I upped the octane from the recommended 87 octane to 89 octane... And everything was just fine...

I then got a K&N performance air filter and it with the exhaust and the 89 seem to make my car act like it did before...

My question is should I keep it at 89 or should I do as the manual said and lower it to 87 again... Thanks...

[Kevin - Blown 95 TA]

It's more likely that the computer needed a little time to adjust to the freer flowing exhaust. Octane wouldn't have much to do with it. Another possibility is that you had some bad gas in there. One thing about the more expensive, higher octane gas is that they put more additives in it which are good for the car, but unless you have bumped the timing or compression, you don't need higher octane. If you have a higher mileage lower compression car that gets all carboned up which raises compression slightly, then you might find that a higher octane fuel might help.

[MaraSport]

Hay thanks...

I was wondering why my car acted like it was when I got it and then started acting weird and now is back to normal... But I guess that is the reason why...

Thanks again...
Mara...