Tiny is right, don't let it idle to long after you run it down the road. When I was drag racing, it was normal to shut it off at the finish line and coast off the track, then read the plugs where it stopped. Thats the only way to get a correct reading for full throttle. If you are wanting a general idea, drive as you normally would, and pull the plugs when you get home. It won't be 100% but will tell you if you are in the ball bark or not. Brown and dry is what you are looking for, or even slightly white. A lean mixture will have small purple spots on the ceramic part of the plug, a very rich mixture will be black and sooty. Oil burning will be wet, black, and nasty.
You need to see if you have a problem before we can tell you how to fix it. Your tail pipe will tell about as much as a plug will. Does it smoke? is there soot when you rub your finger in it? etc...... Joe
