1 sounds like your speed sensor is going
2 no u cnt because depending on throttle and gear(tranny that is) your rpm changes..u can eighter open her up or jus do a lil search and find out..n fyi stock sixxers came with
96 v6 2.73
in 96 they gave the option of 3.08 also
in the 99-04 v6 most likely...