A mechanic on service mechanic on G6performance posted this before:#PIC4536B: Service Charging System Message on DIC and DTC P0621
2005-2008 Chevrolet Corvette
2004-2008 XLR and XLR-V Series
1. Check for aftermarket spark plugs. Plugs that are designed with a "Pulse" technology may interfere with this circuit and cause the Service Charging System message to illuminate on the IP and/or P0621 DTC store in the ECM. If aftermarket plugs are installed, replace plugs with OEM parts. This is not considered a warranty repair and all cost associated with this repair will be the customers responsibility.
Theres other horror stories of them not being setup properly and destroying a cylinder before and lower end needed replaced.I had an 06 G6 with a dead cylinder 3 and had some of these plugs in them-put the delco plug in and ran better than it did with the crapstars