On a related subject, some 740's have been known to suck the intake air hose closed, collapsing the hose and starving the engine of air.

See if your hose has a fold in it where the bend is the sharpest. This hose is available from the dealer or more economically at www.fcpgroton.com (call them if you don't see it listed.)

This connects right to the throttle, and it's a big black bellows shaped air hose. For whatever reason, they seem to fold up given normal engine movements and large throttle application, as on the highway.

Shutting the car off (i.e. relieving the vacuum created) causes it to pop open again and run normally for awhile- it can be a hard thing to diagnose in a shop, since it'll never do it idling.

In any case, it would also be good to rule out the fuel pump relay, but that doesn't sound like the problem with this car.
Good luck with it!
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Rob Bareiss, New London CT ::: Roterande Flakt Och Drivremmar!