nitrous or meth? i dont race the car much but i want the power there when i want it weither i have to turn a knob for a nitrous tune or have meth tuned in.

i have a 2004 comp g gtp with headers, no cat,(soon to put high flow on), gmpp catback into stock muffs, 85 maf, and 3.4 pulley
should i start off with that pulley and go smaller? or what size could i possibly go with? im going full meth no mixing. and getting my tuner to probably tune it