AFC decell trouble

[Big Woo]

First a list of the mods on the car in question.
1990 GS-T
2.5" exhaust
K&N air filter
Denzo fuel pump
small 16g turbo
UICP HKS
manual boost controler
HKS 264/272 cams
Ported head,intake, exhaust (manifold, turbine housing, O2 housing
External wastgate atmosphere dump
550cc/min injectors
2G MAS
Stock BOV vented back to intake pipe.
and an AFC
Compression test results
1 148
2 151
3 147
4 150

timing base set to 10 BTDC

This may be a little tough to explain, and I can't say that it is causing any real driveability problems, but it is anoying and I would like to know whats causes it.

If crusing in any gear and any speed and I back off the throttle slightly. (no much here just enough to cause a slight drop in road speed), and the AFC karman Hz signal reads about 100Hz +,-15Hz, sometimes not all the time, the AFC karman Hz signal will jump from its 100Hz level to 400 or 500 Hz and then back to the 100Hz level. This change in Hz will jump back and forth from low to high very quickly four or five time and then stop. If you let off the throttle more, or accererate the problem will cease immediately. When the Hz signal jumps to the 400 or 500 level the motor gets very rich and bulbery, then the signal comes down and the motor sound fine again.

This car runs mid 13 second 1/4 mile times, gets 27 or 28 MPG, and makes my 80 mile (roundtrip) comute to work each day without fail. Thus far this one has me stumped, as nothing I do seems to help this issue. However I do know that the car did not do it prior to installing the 2G MAF, so I am sure that it has something to do with it.

 

[pneumo]

check all MAF connections to make sure it's not caused by a loose or shorted wire. It could also be your BOV opening irratically- the BOV dump tube sometimes causes some air to flow back up the turbo inlet pipe.