I have an 06 Cobalt SS Supercharged. It sounds like a thump in the engine some what like an atv. It broke 2 of my spark plugs. I get no boost .. idled I'm at -10 when I accelerate it goes up to a lil less than 0 than it goes back down to -20 while accelerated still. I'm not sure what it could be, if some of yall could help I'd greatly appreciate it.