LPG Coversion woes

I have a 1991 735i SE Auto thats done 130K mls.  This model has EML (no throttle cable).  As I do a high annual mileage I decided to have it converted to LPG.  Everything was going fine and the conversion was of a high quality but when I drove the vehicle it kept stalling when you came to a quick stop, i.e. at junctions, traffic lights etc.  Also when you took your foot of the accelerator and coasted around a corner, there was a long delay when applying the throttle again for it to respond (hysteresis).

The guy who installed the LPG has spent many hours trying to find out what was wrong.  At the end of his quest the answer is amazing - if you remove the intake tube that goes from the front grille into the air filter box the problem is cured.  I further tested this and found that if you cut off the 90 degree bend at the end of the tube but fit the rest of the tube the problem is still cured. 

On this  model, the throttle completely closes when you decelerate and the speed sensors & brake sensor indicate to the EML unit that you are going to stop. Air flowing into the grill and across the end of the pipe causes the air inside the pipe to be actually sucked out (venturi effect).  Therefore it is sucking the gas out of the intake pipe.  When you come to open the throttle there is no gas/air mixture in the intake and it stalls.

This effect doesn't occur under petrol because the fuel, cut-off under the same decleration conditions, immediately switches back on under throttle call and injects direct into the cylinders.  Removing this 90 degree bend has also cured a tendency to hunt when using petrol and running on a throttle just open.

Just thought I'd share this with you for anyone considering teh LPG route!