REALLY like this car as you already know. I think if I was you I'd go ahead and put the Holley heads on it along with the ported lower/Systemax upper, maybe toss a TF Stage 1 cam in there if you have the means/time etc., and then tune it and see how the converter acts after the upgrades, I'm betting with the extra power it'll loosen to where it works much better. Turning the boost up as the car sits now may do the same thing as well in regards to the converter. Just my .02.