I have an 89 Prelude Si 4WS. Idle is set at 750rpm, and the engine appears as if it's missing, but it's not. Iridium plugs, nology wires, new fuel filter, and set timing to spec. off idle it screams and runs beautifully. compression also checks out. An ex Honda mechanic told me aftermarket motor mounts can cause a misfire like condition, but I'm doubting it seriously. It's not a big deal really because I know everything is tuned and running great, it's just embarrassing to pop the hood in front of friends knowing i can shake a can of paint on the motor.

Also, I see alot of B20's that have been stripped of the plethora of vacuum lines. I realize the benefit, but i'm curious if there's any downside performance wise to doing this.

 

You should check the motor mounts.