RX048R

I'm looking for an answer the stealership can't pin down. I have an '04 with a 3 month old engine core replaced. All was well until the overheat light and then check engine light started to come on intermittently and then a lazy start. I pulled an 02 code so I took it to the dealership. They replaced the motor mounts (3rd time since '06), cleaned the throttle body (2nd time since '06) and replaced the '02 sensor. I picked it up $1700 later, still with a lazy start (key held in start position and then catches after a 2 or 3 seconds). So they blamed the perfectly fine 4 month old battery because it was only 550 cold cranking amps and didn't meet the Maxda spec of 640. It was fine until the next day and then a lazy start again. Any remedies to this debacle would be much appreciated. Anyone know of a good RX-8 mechanic near Ft. Lauderdale, FL?