Bought a five pack of these modules for my five trucks. 4 worked great. The engines performed just like the ad says. No dash light, no more smoke, oil is cleaner. But 1 didn't work very well. So, we got on the horn with the company that sell this chip and let them know what was going on. We worked through the problem we were having. We all came to the conclusion the chip might be out of range and wasn't working properly. So, we returned the bad chip and the next day we had a new one in our hands. Plugged it in and bam all was good. We are saving fuel on all the trucks which adds up to huge savings. Also in the long run less maintenance cost because the egr isn't working anymore. I highly recommend this product and this company because they stand behind their product. Great customer service.