1998 bmw 318i p1174/code 80

Question

HI,back againe withe the nighmere of code p1174 after i did every shops said i ask smoeone with snapon scaner very advance to check the code p1174 whiche to solve it i did vacume test every where and change the o2&maf &fuel injector test change boots and air filter and my genaric scanner read p1174 BUT the snapon read code 80 whuches scondrey air pump i did replace the rave with six bolt for any air leak cause the pump looks working
but here is the catch it code be the air pump or shut off valve or the non return valve siting the code ..it is alot of $ to replace please need help to narrow it down i have 4 days for my inspiction,,thanks in advance