A quick search didn't return much on the topic, so here is my issue:

I installed high res and re-turned with no issues, except this idle issue.

When I lean the idle out by hand, adjusting the fuel table, I can nicely take the car to 16-17 smoothly without any misfire. However, when I hit the gas and let the RPMs drop towards idle, the car practically stalls (if not completly).

Where should I start?

My MSQ: http://compywiz.com/miata/megasquirt/Jasmine-R-02.msq

 

is your idle setting for "warm-up only" or "closed loop only".

I cant look at your msq on this computer or else I would look at it there.

I had this problem with high res as well, just had to fine tune my closed loop idle.

 

His stock ECU is controlling idle.
Looking at MSQ now.

 

Yeah, I forgot to mention it is parallel, so I don't use the idle control right?

I was writing that before Chad mentioned it but this internet is slow as hell.

 

yea, since its parallel, I am assuming your are letting your ECU control idle.

is there more info on the car? injector size?

 

enrichen and/or raise idle

 

I can tell you just about anything you would need to know, it's a 2001 with stock injectors and home built MS.

 

Yeah that solves the issue since leaning the idle causes the issue, however I rather not have an idle as rich as 12 or 13 afr.

 

You should be able to idle at 14:1 easily with hi-res without that stumble. 16-17 is too lean.

 

Here is your problem. When you hit the gas and let it off you increase MAP and then it drop real low. Your entire lower row of your fuel table is way way too lean. Yes going lean helps with engine braking but you should just turn on overrun and richen that back up to like 16:1 in your target table then let MLV tune to that.
In order to keep your idle stable, you should have all 6 cells either equal or close to each other. My car idles at 26 and fast idles in the 32/36 kpa cell just above it. I make it one VE lower because it runs bette that way. With that lower row all set to those ridiculously lean values, you're basically leaning it out at idle like you're trying to engine brake and the engine almost dies. Richen up the mixture as I've done in this image and I get it doesn't do that anymore.

Your table:

How it should look:

 

Thanks for analyzing it for me chad. Hopefully others will benefit from this error. I will make the changes and let you know how it responds.