I'm not a fan of Mahle pistons, but i can tell you that a friend built a 383" with a street blower, 6 lbs. boost, and the very first time he stepped on it, it broke 6 of the 8 pistons. They seperated at the top ring groove, and the rings had .028 end gap at assmy. I think you might be flirting with danger with any amount of nitrous.
JMO
Zip.