You have to make sure the alternator is charging. Either get a multimeter and check the battery voltage, or remove your alternator and take it to somewhere for a test. Make sure all of it's wiring is clean and tight- and disconnect the battery before servicing it!!!!
As for the running problems, try it again after the battery situation is fixed- low voltage can give weak spark and unpredictable computer and fuel pump performance. If it's still lousy after that, try a full tank of good 93+ octane gas, plus Techron injector cleaner, and replace the plugs. Check the air filter to make sure it's not full of mice (happened more than once, believe me!!) And try a replacement or repair of the fuel pump relay.
One or the other of these things will fix it.
Oh, and since it's a turbo- take a good look at the big black rubber air hoses to the intercooler, turbo, and intake- any holes will cause massive driveability problems, and those mice do sometimes chew holes in them... if the oil doesn't destroy them first. Good luck!!
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total