you will have to have a tuner first of all. If you own a tuner you should have saved the original bin file from your car that way if you ever wanted to go back to it you could...weather it be an emergency or not...so in other words just a back up.If you have a tuner you can usually look on the tuner sites and someone usually has a stock bin floating around.You can deleate the code with a scanner but if the problem is still there then the ses light will just come back on.
Your pcm has low and high octane tables just for casses like this.As long as the low octane table wasent changed then you can put any octane you want in. when ever you want. The high octane table has more timing vs. the low octane table wich has less timing (for low octane gas).Typically people just add timing to the high octane table.Sometimes they also make the low and high octane tables the same that way the timing will stay where you put it at..just depends on the person i guess...thats what i did anyway. You shouldnt have any issues running 87 imho...but then again i dont know exactly what has been done to the pcm...if you can find out what exactly has been done...''timing increased on high octane table 2 deg. across the board''...then i will be able to give you a better answer....but again you should be fine running 87 with your current tune
