Sorry, I assumed 18RG - I had the fuel injected variant (18R GEU) in my RN41 HiLux.
The need for an engineers certificate is - cars manufactured with ADR 27A or greater are NOT allowed to have modifications made to the emissions systems. Now this rule is stepping back a while and there have been amendments to the rules to accomodate engines that come from cars with higher emissions standards than those that the vehicle was released with.
To the best of my knowledge it needs an engineers cert. The best person to speak to about this is an engineer. Look one up and ring them.
As for $200 - it is more like $300. Which is not a lot of money when you consider the reaming that you could get for being involved in an accident and NOT having the report.