In theory the Boss should be faster than that, I think. The wheels are 9.5" compared to 9" for GT which should provide better tire support and more contact patch. The car revs higher and comes with a T2R rather than a T2 differential (I am not 100% sure here) for track pack which means it can utilize the 3.73 gearing much better and no need to oversize the tires. Plus it is stiffer than 5.0 and has better control arm bushings and ball joints.
SCCA's classing philosophy clueless at best. Bunch of us in NER region were discussing or rather venting out how frustrating this classing and pax are and we decided that we should all run in HS in 2015 in Fiesta ST or Golf GTI. The worst part, I feel, is that SCCA puts one/two car models in each class which is significantly better than the others and if you use those car you have tremendous advantage over others. For example Focus ST and now MazdaSpeed 3 in GS, Fiesta and GTI in HS, Boss 302 in FS, Corvettes in AS and blah blah blah. I have started to think this whole classing thing may be ill intended and cliquy.
So I think I can understand your frustration.
The Focus ST in GS is a definite overdog, especially in PAX classes. My local club president, who normally runs an S2K in STR, has a Fiesta ST as a DD, and he may bring it out in HS just to dominate PAX one day.
Want an overdog car? The turbocharged Mazdaspeed Miata is in ES with regular, n/a NA and NB Miatas. It has 40 more HP and 40 more TQ, which is a lot when your total power is 1xx. It also gets wider wheels and almost double the spring rate. They only made about 5000 of them, but it's one of the cars on my codriver's shopping list now that he's given up on STS. Its problem is that it has a really short second gear, think 48mph, so expect a lot of shifting.
Anyway, regarding the Boss, like Whiskey said about the diff. Also, they only get 9.5" wheels on the rear, the fronts are still 9". I novice instructed in one with Michelin PSS tires and got to make a single pass in the car, and while I didn't notice the power (24hp isn't a lot when you already have 400+, especially on a 35sec course), I did notice the stiffer springs, and the balance is really good.
Still don't see them totally dominating though. Boardkat put fancy shocks on his car, I wonder if that would be enough to make up most of the difference. If it's really that much faster, there's always the S550. But damn, they don't make one in GHIG yet

John Ames is the only national guy I know who's actually placed an order, guess I'm gonna have to keep tabs on his results now :whackylol:
One thing I wish they'd do is fix the F Street PAX. Our national champion finished about 400th at nationals this year, and I was around 600th two seconds back. Last year, I was three seconds back in F Stock, and paxed about 400th, with the winner at a more reasonable 150th. Our heavy pigs pay a bigger penalty giving up the Crack than the lighter cars do apparently.
Recently, I asked our local SEB member about the wonky classing, and his response was, um, "I have no idea." Gonna try to ask our local SAC member next, I'll keep my fingers crossed.