hey guys I'm new at this bore/stroke thing, I pulled my head and found out I have pistons that are bored .050 over.
I'm wondering how that will effect my boost, I'm running 15 psi now and it feels like less, is that because of the motor or am I just expecting more than I'm gonna get?

I doubt it's bored .050 over. Usually our engines are bored in .020" increments.

I just happened to buy a set of NPR replacement pistons recently that are .020" over sized. They also have 050 on the tops of them. I'm pretty sure it indicates it's 0.5mm over size, which coincidentally is exactly .020"

Edit: Oh and to answer your original question we need a little more info. What's your setup? What turbo? What injectors? What are you tuning it with? Did you check for boost leaks? Honestly 15psi of boost on a completely stock setup will run low 15's maybe high 14's in the 1/4 mile. Decent but not really fast if that's what your expecting.

Bore size wont change much in our cars. Its not like a big block chevy where you are actually boring out 1+ FULL INCHES. .020" is half a millimeter. Barely anything. Its just to get the bore strait again when you do a rebuild. Effects on boost/power. NOTHING. Maybe a half horsepower if anything.

haha I'm not expecting it to perform better, I'm just interested in what it does, but to answer your question I'm running 550 injectors, 14B turbo, and walbro 255 fuel pump

its 15 psi on a 14b....what are you expecting?