Ok, back with some updates on the situation. I was out of town for a week with work so I couldn't test the car in all aspects. Last night I had a few runs with two of my friends, both E36 320i. One of them has the engine running perfectly with 15'' alloy with 195/60. The other one has problems with vanos, the engine does not run very well and has got 17'' wheels with 245 tyres. We usualy run from 50km/h to 180km/h.
Before the swap, I only ran with the second one, that is not working very well and has got big wheels. It used to go 3 car lenghts ahead. Last night we were perfectly equal two times till 160km/h, and one time my nose went ahead went ahead 2-3m at 180km/h.
With the first 320 that was properly running he went ahead 2 car leghts, I do not know if the car has resoft or any chip. Probably not. I wonder what the difference would have been before the swap. Shameful I guess

I still dream to the day when an M42 will beat a perfectly working straight six, of course without supercharging it.