regal?? i bet the ecu light aint wired up
i got a corsa off a guy few years back with reciept from them for £££££ and the wiring for the let engine was terrible, its a very easy conversion too but they did a crap job, it will be something simple mate they usually run very well
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Yeh they do have limp home mode, can unplug most sensors and they will still run.
check to make sure ecu light is coming on when ignition is switched on, it may not be wired up right.