This would be the same 3.6L 256-hp V6 found in the G8 V6 sedan, and would have the same 17/25 mpg fuel economy as the V6 sedan.

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Pontiac’s G8 line-up may just grow to include a high-performance coupe which bears the GXP go-fast moniker shared with the GXP sedan. This would include much of the same hardware, including the 402-horsepower Corvette-sourced V8 and six-speed manual transmission, and give Pontiac the firepower to compete with the Ford Mustang GT500KR and Dodge Challenger SRT8. GM is reported to be having an internal conflict on whether or not to build a G8 coupe, which would be based on the recent Holden Coupe 60 concept car shown off at Australia’s Melbourne auto show earlier this year.

If it gets the green light for production, the coupe would be available for sale within three years, according to Inside Line. Main reasons for not building a G8 coupe include the looming stiff CAFE standards, stringent emissions limits and ever increasing gas costs. A GM insider speaking to Inside Line indicated there is less than a 50 percent chance of the two-door G8 seeing the light of day. “The G8 Coupe is not dead,” he said. “This is an uphill battle. It shouldn’t be. But it is.”

A GT version of the coupe mechanically similar to the G8 GT sedan would also be likely.
Sources from http://www.leftlanenews.com