the car has 108,852 miles on it it is a 2000 GTP Olympic Edition. jus recently bought it but it does have mods done to it such as a chip (not sure what kind), cold air intake, high performance fuel pump, and SLP pulley with SLP loudmouth exhaust. im not sure when the last tune up was like i said jus bought it about 5 months ago and this has never happened it has been a perfectly good running car no problems what so ever. i do change the oil regularly and always make sure it has all the fluids it needs since ive had it it has been very well maintained by me not sure bout how the owner before took care of it tho. And no i do not run 91 octane in it i was not told to by the dealership i bought it from is that what should be in it, if so what should i do about this?