I have 102K miles on my 98 ML320.
I experienced the P0170 and P0173 codes as diagnosed by the dealer last November. I replaced the MAF at that time with a new unit ordered online. ML ran fine until lately. I am again getting these same two codes.

Could the MAF have gone bad so fast ?

I didn't see any visible vacuum leaks.

Symptoms are 1) takes lots of cranking to start when cold, 2) occasional backfire (at intake) when cold, 3) seems llike lower than normal power, 4) mpg indicator readings are lower than normal.

I used the laptop OBD-II code checker, just shows these two codes with no pending codes. I copied some of the sensor readings from the screen called " current powertrain diagnostic data"

$04 load pct = 19 to 24
$05 ECT = 108 to 145
$06 SHRTFT1 = -14 to +1.5
$07 LONG1 = 35.2 steady
$08 SHRTFT2 = -11.9 to +3.9
$09 LONG2 = 35.2 steady
%OB MAP = 9.8 to 10.7
$OC RPM = 742 to 819
$OD VSS = 0
$OE SPARKADV = -18 to -9
$OF IAT = 64 to 68
$10 MAF = 0.583 to .778
$11 TP = 3.5 to 3.9
$12 AIR = OFF
$13 O2SLOC = SEE
$14 O2S11 SHRTFT11 = 0.095 to 0.765
$15 O2S12 SHRTFT12 = 0.500 to 0.825
$18 O2S21 SHRTFT21 = 0.095 to 0.760
$19 O2S22 SHRTFT22 = 0.515 to 0.830

From another screen called "on board monitoring test results for non-continously monitored systems", I copied the failures :
TID=$09 and CID's = $01, $06, S04, S02, S05, and $03

I'm not sure what to conclude from this.
Any suggestions before I order another MAF ?

Thanks, Alex