Hey guys this is my first post, I'm wondering if the exhaust manifold from a 3SGTE will fit onto the 3SGE. I found a set of custom made headers cheap and hope this'll work as it'll save me a lot of $$$ having them custom made myself.

For NA or for FI?

I'll let someone else go into the specifics (mainly cause I'm tired as hell), but no. It won't fit.

the main thing is the runner length and the fact that they merge into a turbo flange will make them highly unsuitable for an na application, I would almost garantee they will cause a power drop over a factory na exhaust manifold. if you wanted to find cheap extractors for a 3sge, you'd best look on ebay, or companies like pacemaker, hurricane and genie. if you didnt mind modifying them slightly, you could probably make a set that suit an st162 celica fit.

Definitely going to go backwards with a turbo manifold. A tuned turbo manifold is designed to increase gas velocity to make the turbine spin faster, tuned NA headers are designed to maximise flow to improve scavenging of the cylinders.  They're almost opposite purposes.

The stock N/A headers are beautifully designed as is why would you want to replace them.

i lol'd

The stock SW20 headers look great! I thought for a while maybe there was a model that came with cast headers but seems they're all mandrel equal length steel tube! Unless you're changing the lengths (ie 4-1 headers) I doubt you will achieve anything at all and certainly wont hear or feel any difference. The only thing you could possibly do by changing the headers is move the power band. The fact that they're mass produced will have little bearing on the net outcome, its a mandrel bent pipe, machine welded, pretty basic and I dare say probably better quality than most after market alternatives. 
 
That said, what do you want for your stockies?
 
HIJACK, has anyone tried fitting the SW20 headers (with the correct flange of course) to an AW11?

^ nail on the head,
the only good performance proven aftermarket that come close the construction quality of the oem headers, are the fujuibutsui ones,
you will only move the power band, and why would you want to? its perfect, theres a reason why toyota spend alot on RnD and construct them a certain way, buy a set of cams and drop them in, and spend the rest on a cheap 2.5 inch hi flow cat and cat back, be enough noise coming out of it then,

if anything you will lose performance by the new headers running to hot and without the shields from the standard headers will heat the engine up and oil more, put more heat into the intake piping,
a waste of time and money for 2-5 hp and a little noise

a good quality hi cat and 2.5 inch mandrel bent exhaust cost me 600$ and netted me dyno proven 12 kws
plus gave it a deep growl,

the ported and polished intak runners alone netted me 6kw. 
bit of food for though.

worldwalker
The stock SW20 headers look great! I thought for a while maybe there was a model that came with cast headers but seems they're all mandrel equal length steel tube! Unless you're changing the lengths (ie 4-1 headers) I doubt you will achieve anything at all and certainly wont hear or feel any difference. The only thing you could possibly do by changing the headers is move the power band. The fact that they're mass produced will have little bearing on the net outcome, its a mandrel bent pipe, machine welded, pretty basic and I dare say probably better quality than most after market alternatives. 
 

I am afraid that if you are talking about the stock 3SGE headers they are not mandrel bent, and the pipes are not equal length. (The number 1 pipe is 180 mm longer than the others). As well as that, the collectors are not smooth inside.
But apart from that they are well made for a mass produced item.