Bro, I have swapped in a 1jzgte vvti single turbo with its original autogear box a340e with minimal alteration and no check engine light in my daily runner w124 and is MA running very much smoothly. You'll get around 7-8kmpl (city) if you drive with a light foot.
In your case only problems that you could face in case of vvti swap are:
1. Mounting intercooler
2. A/C request for idle up if your car doesnot have MUX output from climate controller (car doesnot stall but idles a bit low, that could be modified with a 8mm throttle bypass via vsv)
3. Power/normal button interconnection would be a little problem without MUX output. (btw it doesnot matter alot without it you would be driving in normal mode and in WOT you would be shifted to power mode)
4. Speedometer interconnection if yours is not MUX operated (you can get speed sensor reading by tee-ing tailshaft vss or teeing a from abs outputs)
5. About ABS working I dont have any idea as mine had a dedicated ABS controller which doesnot use original ECM.
In case of non vvti twin turbo swap problems 2, 3 and 4 might not exist (for non MUXed I/P, O/P) or exist (for MUXed I/P, O/P).
I recommend you search a bit about swap in your particular car and end up for vvti if you have MUX'ed O/P, I/P or otherwise nonvvti tt.
VVTI single turbo is smooth and better in stock in terms of smoothness and power while non VVTI twin turbo is better if you plan to go for around 400hp and up modifications.
Hope this helps.
