Audi A3 1.8 (non-turbo) 2001 with issues........

Hello to all new owner of an Audi A3 1.8 Sport 2001 (non-turbo) 128k miles seems to have been serviced every year etc only thing it hasnt had done is timing belt and water pump. I have issues and of course questions.........So onwards I go.......

Right the car from the off idled badly and would fluctuate when sitting at lights etc also there seems to be an odd vibration/judder that only happens between 70 - 80 mph.....The car also sometimes feels like it's lacking in acceleration. Also I know there is either something wrong with the Thermostat or the Coolant temp sensor as the Temperature never seems to come off the 60 mark unless I am in traffic for a long time where as far as I know it should be sitting happy around 90?

Anyway I got around to running some diagnostics and pulled some codes out:

16486 or P0102 = Mass air flow meter.

16500 or P0116 = Coolant Temp Sensor.

17978 or P1570 = Immobilizer issue.

17852 or P1444 = EGR valve.

16514 or P0130 = Lamda sensor.

16497 or P0113 = IAT sensor.

Right bit more info I tried to clean the Throttle body although not very well and I have replaced the MAF under or near the MAF it looked like a vacum pipe of sorts has been cut. I also changed the Coolant Temp Sensor to the green 4 pin upgraded one. Right soooooooooo The temperature of the car hasnt changed so Im guessing that I need to change the Thermostat as the Coolant temp sensor didnt do the job. After changing the MAF to a new one now the car cuts out yay! sigh........where the idle was bad now it is so bad that as soon as you start the car the idle dips so low as to stall. it was kind of running when I first changed it and had the car warmed up but once turned off and left to sit there now the car doesnt stay on unless you hold the revs using the accelerator.

So Idea's please as I have been all over the net and Im lost nothing seems to be helping me.

Cheers Gav.

P.S There is a chance that some of the above codes are old or have never been cleared from previous work for example I cant see how there is any issue with the immobilzer?