Torque converter affecting idle question

Not only possible, but probable. It is one of a list of most critical components in your combination, and one that will give you incredible bang for your buck. I would strongly suggest that you use a custom built converter from Precision, Ultimate or one of the other builders recommended by the veterans on this site.

It may cost a bit more, but the results, day-to-day enjoyment and satisfaction of driving with a well-matched converter can not be overstated.