Hello Mods,
Please delete this thread as the problem was solved with the battery reset method.

 

I know you said you checked all vacuum lines but double check again was it stumbling like this when you first put the tune on or after you did some pulls also it's a FE so not sure if the problem is still there on the later evo x but check the vacuum hose to the fuel pressure regulator it's a common problem.
Second do you have a boost gauge what's the vacuum reading at I would also toss a new set of plugs in to rule that out also

 

Solved with battery reset.

 

I've seen cars lean out I mean you where a little on the lean side but not to much my funny thing my evo 8 was tuned at 11.6ish wot the car jist responded better in that range by any chance do you have the completely stock map to put back on it ?

 

Also I would do an ecu reset so pull the negative off the battery pump the breaks a few times hook the battery back up fire the car up and let it idle for 15 minutes with no throttle input at all then drive it and see if it helps

 

Solved with battery reset.