Tool Suggestion

I had to perform yearly maintenance on a new customers house. Out of the 3 furnaces and one boiler, 2 were Fraser Johnson(York). When trying to get to the flame sensor out of either both were jammed in the back and almost impossible to reach. Due to the flue pipe design and gas pipe design, I could not remove the blower motor or the flue pipe to make the screw easier to access. Basically tried everything, various forms of pliers, 1/4 inch crescent wrench, Klein slim tool and the only thing that marginally worked was the ztool it took 1hr30min-45 min just to complete those 2 furnaces. As the title suggests any recommend tools to help when I have to come back here next year.