[V6-12v] Intermittent CEL - 2002 A6q V6

[ZZracing at aol.com]

I have monitored this list for may years, rarely contributing (you guys 
know more that I, and I usually find answers in archives).  Car is 2002 A6q 
Avant V6 3.0, 92,000 miles.  I am totally stumped by intermittent drive 
problem: car will suddenly feel as if it has not gas (no response to gas pedal), 
then suddenly resume or do heavy acceleration (like too much pedal).  When 
this occurs, it will generally show the ESP light first, and, a bit later, the 
CEL.  As long as ESP and CEL show, the car will drive well.  Sometimes, the 
ESP light will clear, after which the car will throw a hard downshift when 
coming to a stop.  If I clear the codes, problem returns within 4 or 5 miles.
I have replaced fuel pump and fuel pressure valve, and a few vacuum lines 
which looked a bit dodgy, with no improvement.
VAG Com shows:
16485 - Mass Air Flow Sensor (G70)
             P0101 - 008 - Implausible Signal - MIL ON 
16685 - Cylinder 1
             P0301 - 008 - Misfire Detected 
16688 - Cylinder 4
             P0304 - 008 - Misfire Detected 
16891 - Idle Control System RPM
             P0507 - 001 - Higher than Expected. - Intermittent 
16490 - Manifold / Barometric Pressure Sensor (G71) / (F96)
             P0106 - 008 - Implausible Signal 
17550 - Load Calculation Cross Check
             P1142 - 002 - Lower Limit Exceeded - Intermittent 
Readiness: 0000 1100
 
Any ideas?  Thanks in advance.
 
Dave Zube