From what I've gathered the capacitor is more for higher out put motor's in an attemp to keep the speedo cooler. And make the out put of the speedo more responsive. When I ran stock 27 or 19 turn I never ran the capcitor. The speedo never got hot enough. You can get pretty high tech when it come's to speedo's and The capacitor is more of a speedo protector, more than a benefit to the motor out put. 27 or 19 turn I would use it. I would recommend trying it both way's though. If it feel's like the speedo react's faster it will seem punchier. Exsperiment, exsperiment. QC2 Speaking.
Honestly I would say it would have to help in stock 27 or 19 turn.