If it has a knock sensor then yes.
I don't think they run as lean as possible, if that were the case people wouldn't be mucking around inside the AFM to lean them out (not recommended). Toyotas seems to be tuned rich and in the case of turbos, excessively so. 
 
 

Tree

Hmm that is interesting cos they say production cars are made to run rich...also shouldn't the ECU retard the ignition timing automatically when it starts to knock? I read somewhere (Toyota source) the ECU runs as lean as possible until it knocks then retards until no more knock.
Also instead of a retune, can't you just reset the ECU if it's small changes to the air fuel ratio? ie for intake/exhaust mods?

From the many dyno sheets i've seen in the past of stock Toyotas they have always been severely rich throughout most of the rpm. I'm not so sure the ECU can run as lean as possible safely without a Wideband, it does take in measurements from the o2 sensor but under wide open throttle the car takes in its predefined tune.

Hmm this will sound like personalised intuitive retarded logic but if it runs so rich, can we use lower octane fuel? Aus delivered N/A specify 95 in the manual but my carbon deposited JDM N/A doesn't need 98 does it? Compression numbers range from 185 to 195 psi
Also have octane 100 with 10% ethanol around my area :P

an N/A should be able run even on 91 shouldn't it? doesn't it have a knock sensor? timing plays a big part too.

Yeh the previous owner ran 91 I suspect the ECU knocked back the timing a bit. Can't remember how it felt back then. Just installed a new knock sensor (2nd hand, tested by R&T) and new oxygen sensor (old one was original from 1990!) and it's prob just me but it feels slightly stronger. Timing should be base at 10 deg assuming the dizzy hasn't been adjusted since May last year
 
Bit off topic but just got home and noticed that sometimes a bit of smoke coming out the exhaust while driving, nothing while idling. I think it's just carbon. Electrodes are pitch black and I only installed them October last year :( hopefully the new O2 sensor corrects the AF ratio and carbon gets "burnt" off...

I hope its not your top piston oil rings failing like mine.

the stock ecu retards and advanves ign timing in relation to knock etc, but fuelling.
 
most toyota's i've seen (older) def run very rich under WOT and 4000rpm+ NA and turbo.
 
run minimum premium fuel. 91oct is for car's you don't care about in the slightest.
 
 

I've never been a fan of those exhausts on mr2s IMO if it's got one exhaust manifold it should have one exhaust tip. I don't find it ricey I just prefer the way the single mufflers look I don't know why maybe I'm a sucker for fart cans who knows maybe I'm ricey. This Is my exhaust and I couldn't be happier with the way it looks. I just find it has a really agressive look. Although it could definately be quieter....

Thanks for sharing mate. This is actually what mine looks like right now, and sorry to say but I'm actually trying to get rid of this look lol I consider it an epitome of rice due to mine being N/A as well. I guess in the end it's all subjective. And yes I totally agree with you, it really needs to be quieter.
Senol my compression readings are fine and all within 10 psi so I doubt it's the rings. Might have a look over the EGR and PCV that's probably the only thing left for me to do now, I've finally gotten my car mechanically (engine, steering) returned to factory or better, specifications. In other words it's all maintence and RACING now :DDDD
P.S it's taken me a whole year :P

My pre rebuild compression was 195 across all pistons. The oil rings don't create compression. That's what the compression rings are for. All my oil rings were stuffed but my compression rings were fine. Sorry to scare you but it happens over time :/. Mine would also smoke under load. Keep an eye on your oil level.