Why in the hell do people buy new automobiles and then spend the next year
or two trying to make them into something they were not intended to be, and
bitching about it in the meantime?    If the poster wanted a car with 90 hp,
but bought a Yaris with less hp, he has only himself to blame.  It's like a
tall person buying a mini car and THEN figuring out that he hits his head on
the headliner and can't get the seat to go rearward sufficiently?   Did he
buy the car ON LINE, for cripes' sake?   Didn't he check it out pretty
thoroughly before his name went on the dotted line?   I see these gripes
constantly on this newsgroup and others.....and don't understand why these
folks seem to buy cars with all the forethought they'd put into buying a
candy bar or a movie ticket.
But then, some guys decide to marry the girl after a one night stand and
when they're still hung over..........

 Oh nothing much, just breaking the bottom end of the engine - hole a
piston, break a rod...  Which is why you have to do anything like that
carefully and in a controlled manner.

 With due care to create a proper anti-static workstation (static
bench mat, wrist straps, grounded soldering iron and other ESD
precautions), and the right chip extractor and other tools, it isn't
that much of a hazard.  Anyone who works on Personal Computers at the
component level already has the right gear available.

 The car ECU computers are ruggedized from outside static damage, but
when you open the case you just bypassed all the MOV static protection
at the ports, so beware.  Any mistake can easily cost over $1,000 USD
to fix, could top $2,500   Replacement ECU's are not cheap - partly
because they so rarely go bad the prices stay high.  (I'd convert to
Lire or Euro, but I don't want to hear Peppino sobbing...)

 How much is the stock engine output?  If you start at 70 HP, 90 HP
at full throttle is a reasonable boost to expect.  But if the baseline
is 50 HP, they may be asking too much of the engine.

 Watch for visible smoke from the tailpipe at wide open throttle, on
a diesel that is a sure sign of incomplete combustion.  Too much fuel
for the engine speed and load, or not enough fresh air - a restricted
air filter or air intake or exhaust system.

 Whatever you do (ECU computer memory chip or add on signal
converter) get it in writing that the company putting out this
modification takes responsibility as a supplement to the factory
warranty in case the engine has problems, at least for the first six
months to a year.  If you don't have problems by then, you probably
never will.

 That's how we weed out the bad 'fly by night' companies from the
responsible ones - the good ones always stand behind their products.
The bad ones stand off to one side, and always have a ten-foot head
start if they need to run.  ;-)

    --<< Bruce >>--

Bruce's advice is right on the mark (as usual).