Any suggestions for DRZ250 performance

Hey everyone i'm pretty new to riding about 5 mo's. I have an 07 DRZ 250. Not into racing just in the pits and trails for now. My question is how to improve the low end in regards to getting up to speed. It seems like it lags when i fully open throttle. I've read about putting a hole in the airbox to help it breathe. Also adding a new exhaust. But it seems aftermarket parts are nearly impossible to find. Should I start with the hole in the airbox if so where do I put it? Does anyone know of any place to get parts? Thanx for all the help!

thanks for all the replies. I did take out what i think was the "snorkel" the rubber gasket on the top of the airbox. The bike doesnt stall as easily. I will eventually try a new exhaust.