Digital OLED boost gauge

I am in the process of making a small boost to fit in the dash of my MX6. I don't know why this was not a factory fitment, I have a 1990 Capri Turbo that has one, and I think that the Probe GT might have come with one?
I started off by getting this small one, as I wanted something un-obtrusive, and I wanted to put it close to my line of sight.


What I really want is something in the instrument cluster itself. I did think about dismantling the current boost gauge and making it fit in somehow, but a lot a messing around.
I wnet looking and found this, OLED digital single boost gauge. Looked pretty much right for the job, but by the time shipping was included it came to NZ$180. I could live with this, but decided to see what i could do for myself. I am able to get the screen alone, they are a common item, and after some searching came across quite a few examples of boost gauges built using Arduino boards. So that is what I have done, pretty cheap to make my own. So far the cost for a single unit is, in NZ$
Arduino Mini Pro 5V (clone)$7.50
OLED 0.98" screen $12
mpx4250ap MAP sensor $25
bmp180 barometric sensor $6.50
5V output DC-DC rectifier $8.30
Plus a few more dollars for the prototyping stuff - breadboard, connectors etc.
Although there are a lot of people doing something like this, on forums and youtube, there is not a lot of actual how they did them, or much code. I have come accross some code examples, but nothing that was written for the OLED display. I have taken what I found as examples, plus a few more examples in the Arduino software, and managed to get a working boost gauge.

Atmospheric pressure. Just a fixed compensation value, my barometer sensor is not here yet for getting the true value.

Simulated vacuum using a vacuum pump. The photo has just caught the last number as it was changing.

Simulated boost with a pump.

My idea is to put this in the tachometer, as there is room under the tach mechanism to fit the screen. I will just remove the paint on the dial face to make a square window to show the numbers through. Another alternative  would be to put the screen in one of blanking plates at the top left or right of the instrument cluster. I did also think about using the rectangular LCD that is most commpmly used for something like this and fitting it where the clock is, but I do use the clock and it is not in line of sight anyway.
I decided to just make the gauge show the numbers for ease of use. There are other examples out there that also shoiw a bar graph as well, and a peak boost number seems to be common also. The peak boost number is easy enough to incorporate, not sure how hard it is to do the bar graph though. Doing other gauges, such as AFR, oil pressure etc would also be doable as well, I have seen at least one example of a wideband AFR gauge.