Still to check if all systems are working fine i would still suggest a tuner. Also to gain max best idea is a tuner. He can go for a milder set up and it will work. If a tuner doesn't know how to handle a old car go on to the next one. They are tuners they understand engines. If they can't figure it out or tell you they can't do it they probably also suck at their current tuning.

Engines work on the same principle there has to be a tuner around that can help you. Belgium? Germany? Its not bad to drive a few hours for a good tune