[s-cars] Stumbling along under load

[Bob Frizzell]

S-guys,
My 93 S4 is stumbling like crazy when under any kind of load. Car isn't missing at idle.  I've replaced the fuel filter and the oxygen sensor.  Ignition parts appear ok although I haven't switched the POS's yet.  Engine check light comes on intermittently.  Boost levels won't get up to normal but that's a function of the bad running car, not the cause, I believe.  Possibly a bad injector?  Any help greatly appreciated,
Bob
93 Canadian S4