As for the better gas mileage i dowt it will do much better maby 12 too 14 town lil more on highway but as for power you will have tons more power the 3.4's have about twice the power the 3.0's have stock and you can easyly as a trd super charger too the 3.4 for even more power.
I dont remember what the 3.0's put out stock think its about 145 too 160 somewhere in there but the 3.4's have 190 horses stock and i think 215 ft pds tourqe and with the super charger it puts it up too 265 horses and if you add the 7th injector option that sprays fuel directly into the supercharger it adds another 35 too 40 horses so if you want lots of power i would deff go with the 3.4.
i had a friend with a 95 taco with 3.4 and 5 speed and with 35's it still had lots of power and still got decent gas mileage with stock gears.
so you really cant go wrong with the 3.4 manual swap.
Good Luck
adam
