Toyota: headers, toyota 4runner, k n air filter

Question
Paul-
I am considering installing a set of Downey headers on my 1990 Toyota 4Runner V6 with automatic transmission as well as a new exhaust system.  I have heard that installing headers on the 3VZ-E engine is extensive work.  I was wondering about how long it would take a professional mechanic to do this job and if you think the performance gains would be worth the money.  I basically want to get as much power and torque out of this engine as possible, so I would also appreciate it if you could give me other suggestions to improve its performance.

Answer
6-8 HOURS FOR A PRO. EXHAUST MAN TO DO.AROUND 500-700 I FIGURE.
THEY MAKE A SUPERCHARGER FOR THAT VEHICLE. IT'S NOT CHEAP THOUGH. THE T.R.D. CATALOG YOU CAN GET AT A TOYOTA DEALER CAN HELP U FURTHER. BUT FROM MY EXPERIANCE I WOULD DO THE BOLT ON'S SUCH AS EXHAUST AND FREE UP THE INTAKE.. K/N AIR FILTER ETC. PAUL P.