Update:

• Checked PCV - ok
• Checked all fuses
• Unplugged Idle control valve sensor - still does the same thing, but at even lower idle. So ICVS working.
• Tried reading codes but no errors came up
• Noticed the throttle position sensor was wrong part number compared to Beams spec. Will look at this next.

My original body harness (with Gen 2 3SGE) was spliced with the Beams engine loom. 
But failure to read codes at all is still pointing towards loose ECU connection I suppose. 
 
I was about the clean the ICVS but there's quite a bit of plugs and hoses attached to it, plus the coolant hoses are connected so I pussied out lol. TB was clean when I opened up but I will sum up some courage to try tomorrow anyways while it's easily accessible. 

hmmm splicing can be dubious... thye tried that on my timing signal wire and it didn't work so well... car would run ok for a little bit then start missing and end up missing and farting above idle and wouldn't rev... they respliced it 4 times ( 2 different shops) and never fixed it.... i ended up having to replace the whole wire....

No wiring guys work at IDB....
 
Who did the wiring for you?

Update:
So I changed the throttle body with the correct throttle position sensor and it miraculously ran smooth :D There was one misfire and CEL flash at the beginning but smooth after that.
http://www.youtube.com/watch?v=1_yox_2KndA&feature=youtu.be
Radiator wasn't getting warm so I tried bleeding the coolant. Seems my radiator (changed at start of the year to eBay special/MR2 turbo) doesn't have a proper bleed valve :/
Started car again and problem came back. Coolant should have nothing to do with this tho. At least we can rule out the timing problem right?