If you're NA there's no need for bigger injectors or reprogramming the MAF. The same amount of airflow will still be coming in and your ecu is programmed for stock injectors so even if you did get bigger injectors it would still be producing 19lb fuel psi....
I have a set of stock 19lb injectors for $25 shipped. HERE
only reason you would need bigger injectors would be if you had an extreme N/A setup with nitrous or you had some sort of forced induction. if you're planning on doing either of these in the future tho you might as well go ahead and get the bigger injectors installed. i think stock injectors make 20lbs of fuel pressure or so. putting bigger injectors in wont cause you to pump more gas into the motor unless you reprogram the ecu to do so you will still be putting out 20lbs
I run 30 lb injectors just cause i like to be safer, but i'm programmed for them. decide ur mods, then u'l know if you need bigger injectors. 19 lb injectors are pretty safe for 145 whp, 24 lb for 160 whp and 30 lb up to about 190 whp or so.