I know it makes a huge improvement on a launch, but will you even notice a stall from a roll? Will it raise your trap speed?

And how much affect will it have on gas mileage? Will it affect highway at all?

 

-I haven't done much testing from a roll with mine yet so I don't want to tell you the wrong thing. I know it helps out more from a slower roll like <30, but I have not really tried it at a higher speed.
-Gas mileage will drop a little bit. Maybe a couple MPG in city driving.
-Trap speed might drop a little bit depending on what converter you get. Some are more efficient than others in the higher RPM's and the trap will remain pretty much the same, but other converters can drop it a little bit. You will still most likely run a faster time because you will get off the line quicker.
-Highway will not be affected at all if you get a lockup converter. If you think about it, most of the after market converters are smaller and weigh less than a stock converter, so thats less mass to rotate. Maybe your mileage would be better on the highway with an after market converter than with the stock converter, but its not going to be enough to really notice.