That was probably the Montego Blue, Half-Bridgeported car.
Rotary engines' idle mainly depends on the porting stlyle, which has a similar effect as cams do on a piston engine. The porting changes the timing of the intake and exaust ports opening, closing, and duration.
For example an RX-8 has 0 port timing overlap, (intake and exaust ports open at the same time), and idles as smooth as a Camry. Whereas some of the more radical port styles have huge overlap and idle at 1200-2200RPM and lope due to a misfire every few ignition events.