Do you need it? No
Should you get one? Yes
The car will run a bit lean with LT's and no tune and you're leaving a good amount of power on the table. Spending the $400 or so is well worth it.
Originally Posted by SJFGTO
FWIW, many reputable tuners will not charge you full price twice if you bring it back with additional mods. I would vote for a tune now.
This! My tuner charges $450 for dyno and street tune, $200 for re-tunes.