OK, so I just bought this 2002 GT. It has just had plugs done, and i did a oil change. It runs great and no check engine lights are on. It has a piggy back chip of some sort with a dial for 3 performance settings. And 1 setting for the stock tune apparently. \the gent I got it from ran 87 in it and kept it on the 1st setting on the dial. He said it was just a slightly more aggressive than stock and you can still run 87 with no issues. I like to run 91 or 94 octane in the Buicks and figured on doing the same with the Mustang. So on sat I filled it up with 91, and switched the dial to the #2 setting. cant say i noticed any difference in the car , but if nothing else maybe the fuel mileage would improve. I drove it all around on the weekend, got on the hiway drove to St Catharines and back. Put on about 200 klms and burned 1/2 tank of gas or so. I took it in for the etest today , and they said it came up as " Not ready " ?? WTF , it was not giving any readings or codes. he said I needed to drive it on the hiway and around some, and flog it a bit. it was not ready for a etest ?? The guy I bought it from drove it from Brampton to Guelph daily. It had sat all winter but, has been driven steady the last few months. Im pissed, $35 for nothing and I have to go back. Anyone ever heard of this?