i have been having a problem with an exhaust manifold leak on my runner, its works out pretty x pensive to get this fixed so i had a set of extractors fitted. Cost 680 au which included mandrel and custom piping from the ext. to the cat. ive noticed a nice increase in power and improved fuel economy. how can u go wrong

There are a couple of drawbacks (maybe unimportant ones)

Increased engine noise since headers are thinner than exhaust manifolds.

Potentially reduced resale value, since many people would prefer to buy an unmodified engine/vehicle.

Decreased quality of the exhaust system, since Toyota generally puts high-quality components into these exhausts.

(overall, I like the mod)

There is more engine noise, only its increased air flow, kinda like if u take out your air filter. I can live with that, I have a 2 1/2" System so its loud anyways.

I actually had a toyota dealer, convince me in to replacing the standard manifold. They where having a lot of problems where manifolds are cracking and warping beyond machining.

Standard manifolds cost more too... much more.

By engine noise, I meant the sound from the engine compartment. Headers seem to make a pinging noise since they are thinner. You can hear each exhaust pulse exit the cylinder.

If you have to replace the exhaust manifold, I don't see any reason not to go with headers. I was just pointing out any drawbacks I saw. I may go that way myself someday. :)