yes marco713 thats true and you do have a 50/50 chance of passing but if you have bigger injectors you might as well for get about it. obd2's have a thing called a obd connector and the on board computer can tell the g.a.s also know as "georgia clean air force" the color of your interior in your car! theres to much to list on a obd2car, as for a obdo or obd1 or the real name is asm test for odbo and obd1 cars all that is is a prob and a dyno and a contact to your ignition system so really the car gets to do the test as compared to a obd2 car the on board computer doesnt care if the car is running clean and running fine the computer still does the test.