Did supra run catalytic converters in 03?? If not, the steam is not normal. That is only normal on an engine with catalytic converters. (Because an engine doesn't create H2O under normal conditions. The CC converts hydrocarbons into CO2, and H20. The heated H2O is the steam you see on the newer boats with CCs)
White/gray smoke/steam and a miss, on a non catalyzed engine, could indicate a head gasket problem. Or it could be something as simple as a distributer cap, and the smoke is just fuel vapor. It could also indicate high cylinder temperatures, and you may want to make sure you are cooling correctly. (Check impellor, kinked hoses, etc)
An engine that is running high combustion temps, will leave a pretty steady trail of gray smoke.
Last edited by Fixable; 07-04-2014 at 8:49 AM.