420A Missing link 420aT question

[Brad Bell]

So i installed a missing link for my 420a turbo, and i had some questions for anyone who has ever ran one of these on their setup. First of all, when installed it creates huge drop in vacuum on my boost/vacuum gauge, because the small hole on the side of the unit acts as a vacuum leak. Not sure if this is normal. Second of all, the engine runs extremely rich sometimes while driving not under boost, around 10-11 AFR. Lastly, the engine also runs very rich while on deceleration, for example going down a hill and leaving the car in gear, without the missing link it runs lean like normal, but just the opposite with it installed. It seems to do its job perfectly however for going into boost, my engine doesn't hit fuel cut anymore and moves from vacuum to boost very smoothly. But as for everything else it just seems odd and not sure if it's normal or even safe for my engine. Please share your input! Thank you!

 

[99-420a]

I haven't used one myself yet. I have done a lot of reading and it seems hit or miss on if they work right. Overall people tend to go with the electronic FCD. Based off what we know about engines we know that normally running rich will wash the cylinder walls. The engine sees the vac leak as the gas being pressed down more and adds more fuel because it thinks you are accelerating. I would wait for others that maybe have ran one first hand for years.

 

[dustyboner]

Missing link is basically a check valve between the intake mani and the map sensor..
Missing link and FCD are both voltage clamps, one mexhanical and one electrical.

Back in the day everyone used them cause it was the only option. Now you have multiple options for engine management, im pretty sure they all support 3 and 4 bar map sensor.