build project running rich

Hi all, recently I got the course for EFI tuning as I may need some of the information in this going forward and using to help to try and understand potential issues and solutions, however I have a bit more of a general question.

I have done an engine swap into a mx5 mk3, the idea was to keep as much stock as possible to avoid tuning as I was/am trying to do this on a budget (that rabbit hole keeps getting deeper though!)

the engine in question is the mazda 2.3 disi turbo, the engine is in and is running, however I have noticed a +20% LTFT and recently pulled the sparks, they only have 200 miles on them and have a bit of carbon build up indicating that the engine is running rich.

I have been chasing down potential issues, I did find a small intake leak and I also possibly (more like probably) have an exhaust leak as it seems a custom flange adapter is not tight enough or the custom gasket is crap. I am working on an upgraded adapter as maintanance on it in its current state is just a pain in the ass.

I know these are both potentially cause for a higher LTFT, however my question is have the modification possibly caused this, or is this more likely be down to the leaks I got?

To find the answer to the above, here is a list of changes I have done.

Cone air filter

intake run to turbo (I have kept the maf housing size the exact same as stock)

longer intake run to intercooler

fmic to replace the stock tmic

longer intake run to tb

top mounted turbo exhaust manifold

custom (probably not optimal) down pipe

removed pre-warm cat

placed the first o2 sensor on the outer curve of the downpipe near to the turbo (probably a little further away than stock)

used an mx5 stainless steel midpipe with the small silencer removed (I am unsure of the original platform exhaust diamater but I would assume its similar if not the same)

used mx5 3 way cat

placed second o2 sensor after 3 way cat

removed shaft balancer and fitted the mx5 oil pan.

From what I understand and learnt thus far is the engine works out its fuel trims from the map/maf/o2/temp sensors, for thesee I have attempted to keep them all in the stock environment so my assumption is that the engines information looks and acts like stock to avoid having to tune it.

If my assumption above is incorrect (it probably is to some degree) what do people recomending learning to fully understand how these changes effect how an engine works?

well I partially answered my own question, doing some research / chatGPT I found tthat theres open and closed loop, so this kind of answers my dumb question of if you got sensors why would you need to tune, makes much more sense

Is the Mk3 MX-5 ECM being utilized? If adding a turbo/engine swapping in a turbo engine, wouldn't the ECM not expect there to be additional air in the cylinder due to the boost pressure?