FIRST RULE OF THUMB BACKPRESSURE IS NOT A NECCESSITY FOR "HONDA" ENGINE DUE TO DESIGN! NOTICE REAL ENGINE TUNERS LIKE SPOON AND TODA THEY SLAP 3" MANDREL ON THEIR ALL MOTOR CARS. BEINGS THAT YOUR CAR DOES'NT REQUIRE RPM TO MAKE MAX POWER THAN 2 1/4 IS OPTIMAL. IF YOU HAD AN ENGINE SUCH AS A B16A OR B18C THAN YES BIGGER IS BETTER DUE TO VELOCITY AND VOLUMETRIC EFFICIENCY. STICK WITH 2 1/4 AND YOU WILL BE HAPPY!