Exhaust popping noise

Wait for the engine to warm up, rev to 5000 rpm, then lift off and enjoy the sound.

 

With the engine off, measure the resistance between pins #1 and #6 (or #5, they go to the same place) on each MAF under the black data cable. Pins #1 and #6 are on the extreme ends of the MAF's electronic connector.

Write down the ohm values for both MAFs.

Use a slotted screwdriver to turn the CO screw under the (usually) blue cap (it just pops off with a little force) on the MAF. Notice which direction increases the resistance and which direction decreases the resistance.

To make your car run richer, decrease the resistance between pins #1 and #6 with that CO screw.

Adjust both MAFs to the same value, whichever resistance value that you choose.

Now test drive your car to see if the popping is less pronounced.

Ideally, you need an exhaust sniffer from a dyno run to show you how much to adjust that CO screw, but going 20 ohms from your current setting (should be close to 383 ohms) should be a good first blind guess if you have no such access to an exhaust sniffer (and it might take a couple of adjustments/drives to get your exhaust note as desired).

If the above doesn't improve matters, you can go back to the original MAF resistance setting that you measured in step 1 above. No harm, no foul.