BMW Repair: bmw cant figure out problem, combustion gases, coolant level

Question
QUESTION: Okay I bought a 92 BMW 325i but i take my car for a spin it will go about half a mile then start trying to die not to mention huge clouds of smoke. But will crank right up and idle for as long as you want. it was trickling gas out the tailpipe but I think i fixed that when i bought a ecu but im not sure because it still does a little but i figured cause it still was in the exhaust from before.
im at my last nerve on this car its had 3 mechanics and none can figure it out its just costing me a fortune. here is what ive replaced plugs/intake seals and boot/starter/fuel filter/coils/ecu/ we did a compression test and it was good.my mechanic tells me that all the injectors are working the ecu i bought i think fixed the gas trickling out tailpipe. but still smokes and makes it about half a mile and starts dying i have no clue whats wrong. please if yu have any ideas

ANSWER: GAS coming out of the tailpipe?Have you checked the fuel pressure? That is your first step in checking!I'm sure it isn't gas,just condensation.If it truly was gas then you need to probably replace the catalytic converter,as I'm sure if there was gas it is ruined.And you mentioned smoke,white,gray or black? each means something different.If it is white then the coolant maybe entering the engine due to a head gasket.Bleack is excessive fuel and gray should be somewhat normal.You need to send it to a garage that knows diagnosis!

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QUESTION: white smoke or gray i guess and yes definitely fuel mix with condensation out the tailpipe but the coolant level has not changed. the car does not run hot. could it be something not hooked up right my mechanic had to take just about everything apart to get to the starter and it ran perfect before that.

Answer
Well I'm sure that since you said you had no loss of coolant it probably is not a head gasket.And yes you would possibly smell like gas fumes(it is combustion gases)What was the fuel pressure? an important question.Also did you clean /adjust the throttle plate when you replaced the intake boot?And replacing the starter in that model I thought was fairly easy.