mk4 boost problems! ecu light on (cam sensor???)

[Giro]

 Hi all
i having problems with my new car
i bought it last week and she was running sweet but the ecu light came on and noticed the boost on the turbo was going mad also the traction control light stayed on until i turned off the engine. this happends nearly every run out
its a 02 plate golf 1.8t gti AUQ (180) engine
looks all standard in the engine bay and has done 68,000 miles with full history
the car starts, ticks over and drives well and you would never notice the problem untill you try and bring in the turbo
when driving at any speeds i noticed the turbo boosting then boost again asif i had taken my foot off the peddle and placed it back down and i have also noticed it was doing this constantly when flying at speed with my footdown on and off boost like a surge
i went to my mates and plugged in the the snap-on computer and he said it came up wid a cam sensor
so i replaced the cam sensor reset the codes went for a spin and notice the car was still driving the same
then i switched the engine off and started it back up and the light came back on
checked the codes and this is what it said:-

17748-camshaft position sensor(g40)
engine speed sensor(g28)
incor.correlation p1340

the next day i had delivery of my cold air intake!
i decided to try and cheer myself up by fitting it and noticed that on the diagram the filter was housed in front of the wheel arch and to me this just looked far to stupid to fit cause of water damage that could happen when going through puddles so i just fitted the filter stright onto the maf sensor, job done
went out for a spin and noticed my standard diverter valve started hissing
then i noticed when i put my footdown the boost kicked in then you could here it hiss then boost again while my foot was flat to the floor

so my turbo starts to boost then trys to dump then boosts then dumps then boost and so on
what is going on???
ive checked all the vaccum pipes looked for bent, broken and burnt out wires changed the cam sensor
i dont wanna start changing parts willy nilly cause i havent the money to go down that road
is this a common fault?
could it be the throttle sensor?
what makes the car turbo know when to boost and when to dump? im sure the turbo works of vaccum and not off the throttle sensor
 

[Giro]

small update today...
decided to take off the diverter valve, check to see if the spring was ok just by pushing it in with a screw driver
good pressure on the spring but noticed the spring while pressing in felt like it was sticking a little maybe but not sure
sprayed with wd40 in the valve while opening up the spring dryed the excess and refitted
on test drive found the boost felt a lot more quicker and holding boost a little longer not to sure tho as i feel im getting use to the car as it is
gonna go for a drive out today to make sure

would a diverter valve fault bring up a ecu code?
would a boost controler fault do the same??

[Giro]

after road test today i still have the problem
around 2500 - 3500rpm is were i notice it the most
if i keep the revs up the boost is good

anyone had the same problem?

ive been told today that the cam sensor needs tobe programed to the car then the codes cleared ifs this true??

[Giro]

update job now fixed! 

new gates timing belt, tentioner and pully came today £60 off ebay
checked and lined up old timing belt and found the timing tobe out by 1 and a bit tooth!

replaced everything and timed up the car took 3 hours checked everything then road tested
cars running perfect  job done