I have An 1986 Rx7 and I was wondering whether I should be using 91 or 87 octane I am just street driving it so I don't need more power I just don't want to screw anything up by using the low octane

 

For NA, use the lowest octane you can find... well within reason...

Turbo, use 91, 93 whichever you can get.

 

^ Octane doesn't increase power, it just burns more slowly to allow for higher compression ratios, preventing pre-ignition. Try the highest and the lowest octanes available, (if your car is an NA) and you'll feel no difference.

 

Stock FCs (including Turbos) are designed to run on 87 octane. Anything else on a stock FC motor is a waste of time and is just throwing money away.

 

ice mark hit the nail on the head ^

 

So my stock Turbo motor should be running 87? Only aftermarket is exhaust, FCD, Intake

 

with the exhaust, intake and FCD you should be running high since youve wandered from the factorys "safe" zone of what the car can do for that octane rating