I a profec b II and a defi d-gauge monitoring my boost

the defi is run directly to the nipple on the UIM

Profec B II sensor line is run to a T before the Map Sensor

It seems to me that the Profec B II digital display always meters higher boost by about a pound than the Defi Gauge but im not positive

- a friend mentioned to me that since the Defi is connected directly to the UIM nipple that is it showing the boost reading After pressure drop thus showing more accurate reading and that Profec is reading higher due to no pressure drop reading

BUT, doesnt the vac line to the map sensor come out of the UIM as well? Should there be a difference? Which gauge should i trust more? Should i T into the UIM Defi vac line instead of the Map line?

 

yes the line does come from the UIM

 

It is very common to see pressure differences between items in the car. My pfc, greddy gauge, and greddy ebc all read slightly different. Just pick one to tune to, and that is all that really matters.

In your case, I would just go off whatever one is reading higher, that way you are protecting your motor from over boosting.