HELP VW JETTA Check Engine Light!?!?!?

Ok I have a 1999 VW Jetta (98 body), no matter what I do the check engine light comes on. I took it to some mechanic and changed the NOC sensor and reset the system and the check engine light came on it read code # 0411 (secondary air injector). So then I changed all the hoses got the system reset again and got the check engine light again. Then the mechanic said change the Air Injection unit which I did and reset the system and the check engine light came on again. What else could it be I have spent $500.00 already I need help??? Anybody have any advice?????

Check the fuse for the secondary air injection pump. I believe its on the firewall next to the coolant resivour, or next to the battery, it has a clear cover over it.

Check the vacuum lines on the intake manifold for cracking.

Check the secondary air combi valve (round silver thing next to exhaust manifold w/ a vacuum line coming off of it.) Check to see if it holds vacuum, if it doesnt then replace it.

I have a seminar problem with my vw. I have a vr6 engine and I've had difficulty accessing the parts involved like the air pump, valve and solenoid. The manual says to access it by removing the air cleaner and alternator but the intake manifold is still in the way. I figured to remove the front end. Is this the right and most efficient way to access the parts?

Check the fuse for the secondary air injection pump. I believe its on the firewall next to the coolant resivour, or next to the battery, it has a clear cover over it.

Check the vacuum lines on the intake manifold for cracking.

Check the secondary air combi valve (round silver thing next to exhaust manifold w/ a vacuum line coming off of it.) Check to see if it holds vacuum, if it doesnt then replace it.

I thought I read somewhere that a check engine light for "secondary air injector" meant the gas cap wasn't closed all the way, or some sort of problem with the vapor recovery system. Although I think that was on the 99.5+