Modern converters just don't work like that anymore. Now you can have a custom converter built that can easily be street driven and flash to 5K on demand if you want or need it to go that high. They are tight for street driving but when they see an instant blip of full torque, they can go into the stratosphere. I would call a good converter company, tell them what you have and what you want and go from there. Certainly it sounds as if you need more converter than you have now. While you say you don't want to have to launch 3K everywhere, I completely understand that. But by the same token, you also don't want the converter so tight that you basically get nothing out of it.