I've got a Toyota Avensis from 1999 with the good old 3S-FE engine. Now, the engine is great for what it was supposed to, namely combining low rev. torque with good fuel economy. The peaking power output of 128 hp is also addicuate, but i wouldn't mind having a little extra on the top, which bring sme to my question. Has anyone of you guys had any experience with modifications of this engine, like chip/ecu, airfilter, exhaustion? If yes, how much extra could i expect?

The FE head is very restrictive!

If you want more power, swap it for a 3S-GE or 3S-GTE. Do a forum search for "sorted Avensis"

I'm not looking for a head or engine change. Just wanted to get the peak power up to around 140-150 hp. That isn't asking for much. The tourqecurve is pretty flat from 2000 to 5000 rpm, so no problem there. Just wanted a little bit of extra power on the top, without loosing too much on the low end.

But then again. Say i did swap it with a 3S-GE. Would i have to change the transmission too?

I know the engines are similar except for the head, but what i mean is, would the clutch and transmission be able to withstand the extra power?

Not ideal, but it would work!!!

Use a fast road clutch for a 3S-GE and you should be able to get away with it!

Hmmmmmm, today i read something about modifying the air flow meter, so as to tricking the ECU. Would that work or does the 99 3S-FE use a MAP sensor?