x5 3.0d 2001 issues

[lewisredfern001]

guys/girls
i have just purchased my 3rd BMW a 2001 3.0d x5. now to cut a long story short, it had a fire behind the dash, my friend purchased it from auction years ago and also purchased another x5 which was beyond repair just for interior and loom and electrical control units for all the individual components in the car, which there are loads!!! so it has all been put back together but still has a few faults which i need help in solving. so basically in short it has a different ecu, different clocks and a few other electrical units. but he did however buy a complete new loom from bmw including fuse board.
these are my faults
the speedo - indicators dont flash inside but work outside (bar one which needs a new bulb)
pixels missing - i understand this is a case of having the ribbon cleaned/replaced
when pushing the end of indicator stalk all of the consumption, mpg etc dont work but the Range does.
the rev counter, water temp and fuel gauge all work.
Heater and Fan - it doesnt blow atall, however all the display and controls work. the FSR was found disconnected when
checked last night but after re-connecting it still doesnt work.
Stereo - there is no display and no control over it atall, but sometimes the radio will come on for 2-3 secs then fades off,
when there is sound it doesnt respond to any buttons
Gearchange - this is a weird one, on the speedo it doesnt tell you if your in P N D or R however they all do work in a fashion
Park works fine, neutral works fine,reverse is fine and feels very responsive when you put your foot down but
Its Drive that worries me a little. when put in 'D' its pulls off but very slow, but when you get moving it pulls
really hard all the way up the rev range however it doesnt feel like its changing gear? but it drives fine and
doesnt feel like it needs to change gear and the mpg ive got over the last 200miles is about 25mpg. its feels
like its in the correct gear but it just doesnt kick down when you floor it. also when in manual it doesnt
change gear.
and thats it for now!! my other half has just given birth to my little boy so havent got loads of time to search the forums, however i have looked briefly, but basically what controls units control the above systems that i am having problem with as these are the 1st things i am obviously going to check.
Another theory is that as i have a mix and match of control units and speedo and ecu, do they all need to be linked together within the car?
thanks in advance
Lewis