I owned a 08 Tacoma PreRunner V6, if i was to install a K&N filter and a performance exhaust to this truck, would this increase its fuel efficiency in any way ?

Most of the time no. The more air you get into and out of the engine, the more gas it will use.

ok thank you ,and how about the performance exhaust alone, would that make any difference or would it stay the same as far as fuel effiency?

To get more power, it requires more fuel, or some increase in efficiency. An increase in efficiency is something like correcting for a fueling problem by adding a chip or reducing drag from the air. Flowing more air through the engine by intake or exhaust, is going to require the computer to add more fuel and that will drop your MPG.

The only time I have seen some intake or exhaust modification help raise MPG is if it was fixing some existing factory problem. An overly restrictive intake or plugged exhaust. The engine was working too hard trying to overcome this and using extra fuel. Most modern cars/trucks don't have this issue. Adding an after market exhaust is just going to change the noise it makes at best. At worst, your MPG will drop and your wallet will still be lighter.

"No" to both questions. What's more, a K&N filter will let in finer particulates into the engine increasing piston ring wear. That's why you see a lot of these suped up cars burning oil and their rear bumper black with soot.

For your reading enjoyment:

http://mymiata.paladinmicro.com/K&NComments.htm

Well thank you to all of you,i really appreciate your input, thank you again.