If Woolwich Racing offers tuning then it's legit.
Tuning for performance, either within the on-board fuel map or by a supplemental add-on unit, in-lined with the stock ECU... sure, that's legit. Should anyone want to tune the fuel map on an ST1300, have at it, I bet you £1 that you'll need a magnifying glass to notice the difference on a dyno. Modify the air intake and exhaust, and I still bet you won't see much of a difference - unless you're investing more money on tuning that police departments spend on buying whole fleets.
Tuning will not ever remove any persistent fault code though, and nor do Woolwich make any claims to that effect.
Several people have ventured down the path of disabling/resetting persistent codes - on a jetski, I wouldn't give a damn about an FI warning if that's because I've tampered with the ECU.
Just to re-iterate, the only method that has ever been known to have any measure of success, if you encounter a Code 25 or 26 on an ST1300 (regardless of it's age) - is to replace the ECU with a Honda OEM ECU that has never seen the fault condition. They're cheaper on Ebay, but you take your own chances with buying things from Ebay.
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