I have not run a production version ST engine yet, but have ran some of the same "parts" that will be in the engine. The top end performance is better on the ST engine, as for the standard engine we've been running for a year now here is what I see.

Yes, the stock engine will not compare the same to a ninja or speed on a 200ft straightaway, but how many of those do we really race on?? What I have been happy about over the last year is that I haven't flamed out of any mains engine related, my tune is always where I want it, and the motor is smooth enough to run consistent laps and time jumps. I judge an engine based off how average people will perform with it, not which top pro wins this week with what engine. Every person locally that has run the engine has gotten faster lap time wise because the engine is drivable and has a power band they can use, idles great and they finish races.

As for those concerned with "top speed". Most cars will benefit from going up one tooth on the clutch bell from what they usually run. The team drivers here in the US mostly run the 2035 because of the bottom end and mid range this pipe gives suiting our tracks. I tested the 2039 a while back and the pipe does help with top end on large tracks, and I have noticed some of the EU guys starting to list this pipe on setup sheets. Although I only carry a 2035 and 2039 with me to races, I have seen local guys use 086 and 2013 with good success. Between the combo of gearing, pipe, and a rear ceramic bearing, the top end of the engine in stock form can be competitive enough to compete at high levels.