Since the weather has turned colder her in Va I have been getting a random P1498 EML code, so I have replace the Intercooler boots and the code has popped up again. I can clear it out by re-starting the car and it may stay off for days or hours. it seems to happen most just after start up and in the first few minutes of driving and not after the car has been driven for a while. Any advice?

 

I had the same exact issue. On a cold start the car would throw a P1498 and EML light. It ended up being a bunch of different vacuum leaks; I think what really solved it was changing the o-ring between the BPV and intercooler horn. I actually ended up putting the car into service mode and pressure tested (also used soapy water) and found a few more leaks. My supercharger duct was also leaking at the seams (only 2 months old) so I coated it with RTV all around the seams.

My recommendation would be to do a pressure test / smoke test (either one, use water to check for leaking air).
I ended up changing these:
Intercooler boots, Oil cap o-ring, throttle body gasket, BPV to intercooler horn o-ring, fuel pressure regulator vacuum line, and a couple other vacuum lines that I replaced with some vacuum hose from the auto store. I also cleaned the throttle body and BPV to avoid any sticky operation.

I will add that before I did any work, the car made almost factory specification of vacuum on idle, so this code seems to be triggered with very small amounts of leaks. On a different R53 we found an actual crack in the supercharger duct; so it just depends on the car. On my car I could make the code stay away by turning the air conditioner on with a cold start. This seemed to be enough of a change in the car's idle to fool the computer into thinking there were no vacuum leaks.

 

Thanks for the great advice. This gives me more stuff to check

 

I have looked at the BPV and when the motor is off the plunger arm is fully extended. When the motor is running at idle the plunger arm is fully retracted. At any rpm up to 5k the arm stays retracted and when you take your foot of the gas and the motor goes back to idle nothing changes. The plunger arm is always retracted when the motor is on. This does not seem right to me

 

It does not seem correct. When the motor is off does the plunger arm on the BPV have any resistance in movement or does it move with no effort? Mine has some resistance and I believe it should.