No problem. I have sent this same info to about 10 people who had old threads about noises in the same general area as the VANOS. For 5 of them, it was the source of the noise. One other mentioned that the noise was on the drivers side, and I directed him to his DISA valve, and sure enough, his was falling apart. So, when I see mystery noise posts, I post this same info, because it is an easy thing to check, and it is a really easy fix as well. Plus, it has helped 5 people who were considering replacing their VANOS. So, it was worth a shot.
I know you are inclined to think that It is related to the other work you did, but I would start with the cheapest/easiest checks and fixes first. It could be a belt drive issue. Either one of the tensioner or idler pulleys could have a bad bearing, or the water pump may be going bad. The easiest way to check this is to remove the drive belts, and turn on the engine for a short time, and see if the noise goes away. Start with a dead cold engine, and start it up and quickly check for the noise. If it is there, then shut the car off right away. It will cool off again while you remove the belts. Then, start it again, and see if the noise has gone away. DO NOT run the car for more than a minute or two. Have the A/C on, and turn the wheel a little, since you say it seems to happen when these things are on. But work fast. You will be running with no water pump, and no alternator, or any other belt driven system. I would say 2 to 5 mins, max. Maybe have someone sit in the car, ready to kill it as quickly as possible. If the noise goes away, then it is likely a tensioner or idler pulley, or the water pump, A/C compressor, or the alternator. This method may cause some CEL codes to show up, so I would only do it after probing around the belt drive components as much as it is possible to do safely. It is a last resort to rule out a belt drive noise.
You may want to look in to the CCV system, if it is original, and your car is over 60 to 80k miles. It is not very likely that it is the cause of a noise, but it is possible. Search the Forums for more info on how to diagnose this. Or, maybe someone else will post some info in this thread about this.
If the noise is still there, then it may very well be the VANOS. Look up some diagnostics for testing that. Also check out*
http://www.drvanos.com/ They have some diagnostic info on there as well.
I also think that they have one of the best deals for VANOS replacement. For $250 (after you return your core, they refund $150 of the $400 initial purchase price, so it is only $250 in the end), you get a remanufactured unit, that is better than the factory original. I have read about their units in several BMW magazines, and they have all said that they are better than OEM. You can find some of those reviews online.
I know that some people will jump on here and say that they installed one of the rebuild kits available, and they work great. Maybe you want to go that way, and there is nothing wrong with that. But, for $250, you get a unit that has been completely disassembled, and brought back to better than spec, by people who do nothing but rebuild VANOS units for a living. Also, they verify that the complete unit is up to spec, not just certain parts, and they use better than OEM tolerances for the bearings they replace. To me, that seems like a great deal.
I think some of the repair kits are band-aids, that stop the noise for a while, and do not address all of the design flaws with the VANOS unit. The Dr VANOS replacement is a complete solution. And if your car is low milage, or you don't plan on keeping for several more years, then the kit may work fine.
I will be replacing mine with a DrVANOS unit, in the next 6 - 8 months. It comes down to what your budget is, how many miles your car has, and how much longer you plan to keep it. All of that will determine what solution you think will work for you.
I want an improved, complete solution, done by people way more qualified than me, that will last me another 100k miles, and comes with a warranty as well. Sorry for the long post, but I wanted to give you as much info as possible, and point you towards the cheaper, easier to diagnose issues first. I also wanted to point out the pro's and cons for the a VANOS repair, if that ends up being the problem. Plus, it is 4:30am, and I may be over explaining things at this point. o__O Good luck!