i dd my car with a welded diff and know many other people who do also and it isnt as bad as people make it out to be. it is a little more rough but the understeer isnt very bad like people like to say. it does put more strain on the car tho. unless you plan on drifting, i would suggest investing in a lsd. as for the launch, i guess feather it little at the initial launch and use the low end torque of the KA to your advantage(althought this is coming from a drift/auto-x guy)