breaken up on top end

how do i find out what altitude im in i live in lower right side of missiouri

im over in kansas city ks. just outside of mo. an all i have changed on mine is a full fmf pipe set an im running a 250 jet an it seems fine im going to play around with the jets between 260 an 280 to see how that does
 
i would start at a 260... then go up from there and do u have ur air box lid on i would take it off...