Miata MSD Boost Ignition Timing Retard Unit for those without Megasquirt 90-97 turbo
 

Just like the one here with a different looking label: Miata Performance Parts : MSD Boost Ignition Timing Unit : 1990-1997

"Engineered specifically for the Miata, this unit retards ignition timing up to 6 degrees in direct response to boost. The result is that you have your full timing when crusing around but when you hit the boost this unit reliably pulls the timing out in proportion to the boost. We have long liked this unit for its dependability and low cost."

Perfect band-aid mod, pretty easy to install. $90 + shipping.