the G6 GTP manual doesn't sell as well as it could for two reasons
-too expensive for what you get (i.e. pushrod motor, second tier handling, GM typical interior)
-enthusiasts who drive cars with manuals also want the best engine hardware to go with. the 3.6 litre vvt hf whould be in this car, not the 'dated' 3900. the 3900 is not perceived as competitive to the Altima's 3.5 or other cars like the Accord v6, etc.
I'll also add if the car has developed a rep as being a numb handler and lacking steering feel and other chassis refinement, then the buff books will knock it and that kills sales.
The Mazda6 v6/manual sells extremely well. Part of that is because you can get the stick and OHC v6 for a lot less actual money. It is possible to get a Mazda6s v6/stick and just a tiny few options but still get it around 20 grand. Most GTP's rotting on dealer lots will sticker at 28.5 and north. GM is not big on incentives anymore. So your G6 GTP is gonna start around 25 grand. You can say it might be cheaper than an Altima SE-R for example, but just six months ago I could have walked into any Nissan dealer and thrown 25 thou on the desk and walked out with a new base (but extremely well equipped) Maxima that has the GTP trumped on many consumer levels. Add to this the perception that one should never pay as much for a GM car that you pay for other brands and the pushrod factor and the fact that the G6 is still narrow and low compared to the Accord and Altima and even the mazda6 and that's why the G6 manual doesn't sell.
its one of those things where if you build it right and nail everything than having a stick will benefit you. But the G6 now falters on a few other basic levels that affect its sales greatly.
If Pontiac didn't have their collective heads up their asses, what I do is take a base 6 cylinder G6, and offer a simple 'performance' or GT package. the 3.9 engine, the 6 speed (1000 bucks). then i offer a suspension package which includes 4 wheel disc, tight suspension, and the steering upgrade to high perf hydraulic (1500 bucks). if you start with the base G6, one can get one and simply choose those 2 options and get a great high perf value. I would then offer an option for high bolstered seats, but only a few cars. the basic G6 seats are good to begin with.
then you would have your sunroof and sound options.
the G6 would improve its cred 1000 % by simply offering the 3.6/manual combo. Even by selling only 7-10 thou a year. Pontiac IS performance, right?