E28 Hesitation Problem

[MMALSAQRI@xxxxxxx]

BMW 528e 1986,

The car hesitate under load, it feels like if it's dragging a heavy load 
behind, when depressing the gas peddle to floor the car still moves slowly, 
it doesn't pick up fast. Somebody suggested to replace the air flow meter, 
but didn't work, I tested the fuel pressure it seems to be good. it takes a 
long time for the car to pick up speed. lacks a lot of power. the car used to 
give me 27mpg, now it dropped down to  23 mpg. this hesitation problem is 
driving me crazy no body seems to understand what's wrong !!!
the transmission tested and it's good. One thing I noticed when depressing 
the gas peddle to floor the idle start jumping back and forth and the car or 
the engine feels like it's not breathing or choking. The tune up changed 
recently on the car. also the oxygen sensor, somebody told me it might be the 
catalytic converter, I don't want to take the risk and buy one then it turn 
out not the problem, like I did before with the Air Flow meter. Is there any 
adjustments need to be done when replacing the air flow meter?,
is it a sensor problem?

Please send me solutions for this crazy problem.

Thank You
Moe.

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