i got this when i got my nitrous kit and it has saved my ass 2times. now i know you cant use it to tune the car but it WILL show you when you are running lean. like when the defective B&M fpr i had on took a crap i ran lean, now if i didnt have the meter i would have started melting stuff very quick. and when the vac/pressure line from the zex box blew off the fpr during a race ill bet by the end of the track i would have had to get a 70 mile tow but i saw it was running lean and i stopped. i suggest everyone buy this when your running boost or nitrous, not for tuning but for letting you know when your running lean cause of a fuel problem... its the best 60 bucks i spent!