Gurgling

Air hole probably needs opening up a bit, if you do it, do it slow and gentle so that you don't crack the meerschaum lining, best start with a smaller bit and work up to 3.8mm or 4mm if that doesn't work, I always put the bit in a tap wrench a screw it in by hand.

Maybe your tobacco needs to be dried out more. What's the humidity like where you're smoking? Could be something with the internal construction of the pipe.

As Ejames says, internal airflow can cause gurgle. It's surprising how little moisture can cause a gurgle in some pipes. If the airflow is disrupted and becomes turbulent, it can cause the moisture in the smoke to collect at one point. One thing you can try when you first get a sign of gurgle is to blow VERY VERY gently down the stem. This pushes any moisture back to the tobacco where the heat from the burn can evaporate it. If, when you blow, you disturb the ash in the bowl, you are blowing too hard. Also, some pipes just need to be smoked slower than others!

I have one pipe that likes to gurgle mid-way. I just keep smoking slowly and it stops. If it goes out, I let it rest for a couple of minutes before relighting. That helps.

You can also cover the bowl with the palm of your hand and snap your wrist, as if you are trying to shake something out of the mouthpiece. This will almost always clear the moisture.
Obviously you don't want to put your palm over the bowl if you have just puffed, heating the cherry up too much. But in between a couple of puffs, this works very well.
It's a trick I picked up at the VSL.

I had the same issue with an estate pipe a few weeks ago and found that I wasn't tamping it down well enough. When it starts to gurgle I tamp it and no more gurgle.

You might try Nording pipe keystones, I have not myself but the concept is sound.

The solution to all gurgles is the pipe with a second chamber.
Aside from that, what wasn't mentioned, or at least not clearly...
Anything that cools the smoke before it gets out of the stem will percipitate moisture.

Stems are never as hot as the tobacco and percipitate moisture. The longer the stem, the more it percipitates. Metal inside the shank or stem percipitates moisture.

What Withnail said about turbulence is true also. Turbulence is made up of an alternating pattern of low and high pressure gases (smoke), and moisture percipitates from the low pressure gases.
The deeper the bend, the more the moisture collects.

Percipitated moisture has a greater chance of getting out through the stem of a pipe with a straight shank, and what doesn't get out has a greater chance of staying put.

The moisture runs straight down the draft hole of a bent pipe - the deeper the bend the more and faster it goes.
anthony

I GENTLY tap the tip against my heel a few times until the offending liquid appears. Then wipe the tip on my sock and keep on puffing. It's just a habit I've developed and it seems to work fine.