I got my car running absolutely perfect this last 2 weeks and just halls *** and runs great as far as a/f's go all over the map, part throttle, idle, boost etc

But this week i hooked the wideband back up in my car and noticed that when I downshift/ compression brake, the car runs VERY lean, like off my sensors limits lean 19.4+

You can downshift at any point in any gear, I usually do it in 4th to third to slow down and roll around and the rpms are at about 3K, vacuum is in the -22 region. As soon as you downshift and are off both clutch and throttle itll start out @ 14:1 and the numbers just start going leaner and leaner until it pegs out the gauge and I pull it out of gear. Ive tried dumping fuel (15% so far) int the -22 area and its surrounding cells but it just wont richen up

The car is running ng55 turboedit on a gm 3 bar and dsm 450's, first time tuning a car so I may be missing something.

Heres my map if it makes a difference

CLICK!

 

Just think about it for a minute...

Why would you want gas when downshifting?

If you had gas it would ignite and you would not have any compression to slow you down.

 

That's a normal routine performed by the ECU.

It's called Fuel Cut-off Control.
IF TPS = 0%, and RPM > 970rpm (1300rpm for ITR's), then the ECU will shut off the injectors to save fuel during deceleration conditions.