Didn't mean to make the 03 sound so scary... I think it's an awesome bike!
For conditions like MX, I think it could use another 6 oz's or so of flywheel. All 03's are fussy about jetting and run well when dialed in. I ride slippery, tight woods, where the "hit" was a handful. The biggest improvements I made for a more "friendly" power delivery were fairly reasonable... 12 oz. weight (custom made with a alum. side-cover "shim"), V-Force reed cage, Yamaha's 5 mm reed spacer (bolts right up). MUCH more torquey and predictable now, but still WAY fast!