I4 seems to be a very under-rated engine. I've seen a few examples of turbo builds and they seem to work well.

If the I4 had been used by Ford in a few more applications instead of a Zetec I reckon it would be a far more regularly tuned engine.

For the Scorpio engine are you going to run the 16V head from the Scorpio, or RS2000 or make a hybrid with the Sierra 8V head? Supposed to be nice and torquey with the 8V but unsure on turbo builds