Toyota Repair: 1993 t-100, intake leak, conputer

Question
My t-100 gets to 1200 rpms and starts reving up and down and i cant get over 35 mph. I have changed the plugs,wires,dist. cap,rotor button,mafs.,o2 sensor,fuel filter,air filter,with no change can you please send me in the right direction?
DOES this truck have a rev limiter and could this be the problem? thanks

Answer
No, it doesn't use a rev limiter but it has fuel cut which can be activated by the conputer depending on the circumstances,is the check engine light on now or was it ever on before and what were the trouble codes if any? A lot of times these erratic engine behaviours can be caused by a large air intake leak, have the intake hoses been checked for leaks, another possible problem may be that the timing belt has jumped on the gears