I am still trying to figure this out. My daughter's 940 turbo idles OK, but if you try to accelerate more than the slightest amount, the engine starts bucking violently. RPMs drop down and back up. If you back off, it stops. (It stopped doing this at the end of a 200 mile trip, but then returned over a couple of days.)

I have:

replaced fuel filter
filled tank with gas
put in bottle of techron
resoldered FI relay
swapped fuel pump relay
swapped fuel pressure regulator
swapped AMM
inspected all and replaced some vacuum hoses
inspected turbo hoses (replaced one)
swapped coil
checked fuel pressure at rail
pressurized system at turbo inlet (after hearing air under intake manifold, but not finding a hose problem, I replaced intake manifold gasket)
replaced two idle motor hoses

And today: I replace distributor cap and rotor
replaced plug wires
cleaned throttle body, with new gasket
swapped power stage


I then tried to replicate the problem on my 1994 940. I disconnected several air hoses off the intake manifold to create air leaks. It did not produce the same effect


Help! what else is there to try?