Latest issue of Road & Track reports the Opel GT to be sporting a 200hp turbocharged engine not yet available in the Sky from which it is based. They also seem to imply that there are many other changes between the Sky and the GT and that the Sky may get these changes down the road.
As reported on the official
www.opel.com website only one version of the GT will be produced, utilizing the Redline's (and GXP's) 260 hp, turbocharged d.i. 2.0 liter engine. I assume they are confusing the Speedster or TwinTop with the GT.