100kW at the wheels is do-able with the standard ECU.
The highest power city I know of was Angus Buttons "STUBBY" and it was running around 25 PSI of boost from a GT17 (I tihnk maybe t25). Forged arias pistons(It has later been said charles has never seen a city piston fail with good mixtures) forged rods, ARP head studs and rod bolts clamping stock head gaskets down with 10Nm more torque, a boost ignition retard module, factory intake and factory ported throttle body. It was running the factory city ECU with larger prelude injectors, and an adjustable FPR. It had no tune whatsoever and was running like 10:1 mixtures at high boost. They dyned it on a 35 degree day somewhere in oz and got around 200Hp at the engine. With proper mixtures and on like a 20 degree day that sould have been well over that, probably 220-230+.
It is my opinion that you could go about modificatino in a more refined way than charles did and get the same power but more elegantly.
I would:
Make a new intake manifold keeping CVCC and with a single large butterfly, just like the one colza made (but neater
)
Get something like a GT25 that is capable of about 200Hp on its upper limit and doesnt mind around 20psi of boost. Stick it on a good manifold
Get a good intercooler, charge temps are going to be crucial.
Rebuild your engine, make sure its in factory new condition, can re-use pistons and rods but replace everything else.
Port and polish your head, dont make the ports much if any larger, just smooth them out paying special attention to the short side radius.
Get a hot cam, there are still a few places over here that do cams for them, a hot cam is going to shift your power band higher and the HT rod bolts are going to enable you to safely use it, THIS shifting of power band is crucial to making power as power is a direct function of torque and revs, so two ways to make it, increase the revs and keep the torque, increase the torque and keep the revs. You can get so far with the second method but a combination of the two is how its gotta be done in my opinion.
Get a good extra injector controller like a turbo link. That way you can still keep a good idle and off-boost mixtures but when the boost gets serious you can provide accurate fueling, Get it tuned by someone who knows what they are doing and has a wideband O2 meter and a knock sensor!
Ignition you MAY have to play with, I havnt done it yet so I dont know, but you may well have to reduce the amount of advance and gap down the plugs or something, sort this out when it comes to tuning, a good tuner will know whether you will have to. If they dont knnow about CVCC take a printout of the description of it to them, it will help them understand the massive ignition advance.
Anyway im sure ive forgotten shit but at least that gives you some stuff to think about, there are a lot of things you need to sort and get running before you think about aftermarket ECU's. If you get the engine i described above running well on factory fueling up to 15psi and break the motor in. Then start to think about extra fueling and stuff.