I had my computer's rev limiter tuned so i didn't end up needing these boxes. i have a accel 300 plus rev limiter box and a 375 plus muti purpose box with plug and play. Now i bought the 300plus used off ebay from a company and payed $200 for it. i never used it, company i bought it off off tested it after it was used to make sure it worked. the 375 is brand new never even used it yet also. i bought it from summit $200 bucks. you need both of them the 375 plugs into the 300plus. i will sell both shipped for $425.