Nah, a tuner is probably the last thing I would want to mess with. Your fueling is ultimately done in the fuel jet for the most part... if you spray dry then you have other issues.
I would NEVER toss a plog on a nitrous car... the gains would be invisible at best... Get some headers on if you want to, but otherwise a 3inch DP will be more than enough to keep a 125 shot happy.... Exhaust mods are way overrated on this forum for some reason....