more power for petrol 1999 prado

Very little, save your money a buy something worth while.

Trying to get decent power increases with tuning on a normally aspirated petrol engine is very expensive for very little gain, aftermarket chips offer a slight increase in performance but the best way would be on a dyno whereby you can adjust stuff like cam and ignition timing and fuel delivery....fuel delivery is not adjustable on your vehicles unless a differant ecu, aftermarket chip or a unichip is used.

Some other mods like air cleaner, leads and cold air induction may only add 1 to 2 Kw's at the wheels if lucky.

There are exceptions. (example: Varable cam time engines)

Some vehicles like Holden, Ford, Mitsubishi and Subaru and a few others can have there ecu's flashed.

Turbo petrol and diesel engines are a differant story.

Regards Richard

My mate ended up putting on some extractors (Genie brand) for memory and a 2 1/2 inch exhaust/muffler etc and was quit happy with the increase in performance the problem was increased fuel consumption as he liked the extra grunt (I think more the sound) so kept on putting the foot down. I personally didnt like the sound of it and it droned (spelling) too much inside the cab. The 3.4 V6 seem to have quit good low down grunt but not the quickest off the mark. Depends if you want to suck 20L per 100 or 15 when driving around town to how hard you plant the foot. I havnt heard of anyone putting an additional chip in so cant comment, only heard about one in the 1kz t/d was quit happy with the difference. If you really want some go get the 120 series 4L 179kw vvti :-). Regards Steve M