I can't say for sure that sway bars resulted in faster lap times for me. But they do seem to help with making the car feel more stable (less lean) on the track. That has to help with confidence which should result in being quicker.
I've played with a couple combinations and now use '99 Racing Beat hollows set to full stiff on the front and FM on the rears set to full soft. I have the RB sway bar brace also. If your car is balanced now I wouldn't mess with it.
It seems to me that you might just need to have a rabbit to chase. Or have an instructor (one who knows Miatas real well) go out with you and show you the limits of your car. My biggest improvement was when a instructor, who drives Spec Miatas, took my car out and showed me what it could do. What an eye-opener that was. I learn that I was coasting too much into and thru a few corners. Sometimes you can make up more time by not braking too early and getting back on the throttle sooner.
Like my instructor said to me "If your not using full throttle, in a Miata, you'd better be using full brakes". Might be a bit of an exageration but it is something that rings in my head when I find myself coasting thru braking zones.
And start using all of the track on the exit of the turn. If you aren't tracking out under full throttle then you're just not going to have the speed you need on the straights to knock time off your laps. Miatas are a momentum car, watch the good Spec drivers (in the 1 or two corners that you can stay with them). They'll show you how a miata is supposed to be driven.
One last thing. Just keep pressing on and don't worry so much about lap times. You'll improve more when your not looking at time sheets. Find someone who is quicker than you are and work on chasing them down. Then move onto the next faster driver. Repeat until everyone is behind you
