UK Car Repair: vauxhall astra 1.6 16v 1994 wont idle, vauxhall astra, vent valve

Question
my astra starts up misfiring badly then if i take my foot off the accelerator, it wont idle and stalls. my garage said it was the egr valve but i replaced it and its no better. the only breakthrough i had was if i took breather hose(i think its called) off the top of the engine it would idle-still madly misfiring though (which then goes to some sort of control unit which then feeds another pipe off to the map sensor). also have a few ecu codes
33-MAP Sensor (Voltage High)
34-MAP Sensor (Voltage Low)
47-Linear EGR Position
56-Air Control Solenoid (Voltage Low)
61-Fuel Tank Vent Valve (Voltage Low)
85-Immobiliser (Wring Signal)
any help/advice would be greatly appreciated as a garage/alot of money is out of the question for me at the moment thanks.

Answer
From the codes it may be the MAP sensor in the air inlet assy. It runs faster when you pull off that hose because you are allowing more air into the engine. In a case like this I would first check that there is no serious problem by doing a cylinder compression test. If all is Ok try a new MAP sensor. You will need to have those codes cleared!