bigger fuel injectors

I checked my favorite performance VW site NGPRACING.COM They have several injector "sizes" from 30 #s/hr flow all the way to 160 #s/hr. It's gonna depend on what your need is...how much boost will the engine have (turbo or charger). I recommend getting on one of the VW forums like MYFASTGTI.COM and researching in the performance tuning threads to get a feel for what's working for other folks.

My car is all stock and doesn't have a turbo and I herd a nice cheap mod I can add on for improved performance was bigger fuel injectors

Not sure where you heard that...but if you have injectors that put too much fuel in per air charge...the airflow meter and ECU won't be able to compensate and you'll do more harm than good. Best thing for a stock motor is a cold air intake, low-restriction exhaust, high-quality plugs, wires, and coil...good oil and good gas. After that, you can start looking at the little tweaks that will improve power AND efficiency.