I'm not surprised it's noticeably better, and expect you've seen maybe a 25% increase just about everywhere. However, as Leigh advises, it's imperative you check the jetting.

A "bog stock" MC28 with just an HRC card is one of the few things we've had the luxury of testing on the dyno, but I can tell you that the HRC card modifies the RC Valve operation, the ignition, and the air correction (as it's meant to be used with open carbs). Therefore, it's vitally important the jetting's at the very least checked.

There may well be much less of a gap between the stock settings and an almost stock bike with "just" an HRC card, but I would be mind-blown if they weren't different enough to be able to run both cards at will, with no other changes! I expect once set up properly for the HRC card, the performance with the stock card would be noticeably less usable.
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Andy.
NSR-WORLD.COM

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