i have a no excuses 1.6, i mean as much as any divisional guy can have. healthy X factor motor, penskes, mazdacomp diff, etc etc, and i have and do win divisional races in it. even against some of the midwest's best (craft, greenhill etc). never easy, but no win in this class ever is.
my opinion is that 1 on 1 and in clean air, the 1.6 is at least a match for any of the other cars, at most tracks. Road America, probably daytona, and other really 5th gear based tracks probably not, but most club level tracks it certainly competes.
the problem i think at bigger races, is that what the 1.6 does well, does not lend itself to pack and draft racing as well. its strengths are mid corner speed, and braking, which, when you are in a big pack of cars, it doesnt get to show off. the 99 is faster in 5th, while the VVT gets out of the corner quicker. those both are attributes that are very handy in a pack of cars.
a 1.6 both podiumed and won (?) just a few weeks ago in gratten majors against brown and hille, so it can be done. and they are still the cheapest SMs to campaign. from a not having a prep shop do all my support/work/parts, its also probably the best car because it has the dumbest ECU and thus probably the highest electrical system reliability.
put it this way, 2 years ago, i was thinking of buying a 99. after a lot more experience with top 99 and VVT cars in these last two years, i actually am more confident with my 1.6 than ever before. at least at the style and level of races i can afford to run (mostly divisional)