The '92 and '93-94 engines were similar; emissions constraints are responsible for the HP decrease. However, as I understand it the '92 is cheaper to bore out to 6.0-6.5 litres because it is of a "closed deck" design; later engines were open deck.
A chip will give it a tad more punch, but not likely as much as your BMW gained. But I'm sure it'll be fast enough....ANY E500 will absolutely kill a 750iL I assure you, at any speed.
Best regards, Michael