You'll want an F, G, or maybe even H diameter. So NECx or N3Cx - replace x with the diameter you want (F,G,H). I'd try NECG or N3CG depending on the type of power delivery you're after. NE for smooth, N3 for a hit onto the pipe.
reading the thread recommend me a needle, the fella used a N3EG, with good results and is uk based with a similar bike.
im a bit of a sucker for a strong hit lol so NE's up my street lol.
if there cheap enough ill try the N3CG to