It sounds to me like your fuel pump is what is giving you your problems besides the whole V-6 thing, you need to bump to a V-8 because unless you plan to sink thousands into your v-6 you cant drive them like v-8's I have a 91 RS with 138K ran like a champ until I threw a main barring, but now Im swaping the motor with a Vortec 350 with a comp cam kit, 310 RWHP