If you don't own one, I highly recommend owning a good quality 1/4" torque wrench (for 1/4" I use a
Wera and recommend it). You can go cheaper I suppose, my only warning is that a measuring device with unknown accuracy (cheap brand I can't trust) is worse than no measuring device at all. You are looking for south of 10-nm and that's pretty light.
A smidge of blue threadlocker may be helpful. But cleaning out the holes is at the top of my list. Unlike when the VC bolts are installed at the factory, those holes can be contaminated with oil, wreaking havoc on fasterner's performance, not to mention your torque readings (will invariably under-torque with oil contamination in the hole which is a lubricant). If you do an install, clean holes (cover head, squirt brake cleaner in each hole with the spray straw), consider blue threadlocker, and you let the threadlocker cure, you won't need to retorque (if you understand how this works). Some people believe in adding 15-20% torque value to a fastener with liquid threadlocker. Henkel (Loctite) specifically recommends NOT doing so. Q-tip will tell you if a hole is clean.
I personally don't use threadlocker here, nor do I retorque. If the holes are clean, the fasteners are correctly installed, they will do their job, just like they did for BMW.
I worked in two shops over a period of about a decade. I wouldn't trust anyone that is a mechanic and passed tests and received certs. Same in the two other professional fields I worked. Tests and certs are far from an ultimate indicator of someone's competence. BTW a bunch of mediocre doctors pass tests, and paper-pushing lawyers pass the BAR. Better than nothing but if one is deciding who works on one's car because of a cert ... one gets what one's discernment produces. In my current line of work, I spend a fair bit of time acquiring new clients that have had botched work done by "authorized" service people - I'd hazard a guess of 15-20% of what comes in - and I have no certs in my currently line of work, nor formal training in this case (autodidact).
No charging professional mechanic I know will go to the trouble of (in my opinion) properly preparing these cars for a valve cover gasket. Or spend the twenty minutes cleaning out the spark plug holes and threads for debris. 95% of customers would not pay for the job done this way. That's the reality of most of this industry, for which anyone who has actually worked in this industry already knows. Does this mean the mechanic's work will fail? No. Does it increase the odds of failure (premature) - absolutely.
Not criticizing anyone here that has done a VC install. Doing an N54 VC install is tricky enough to get right with a stock VC. One's odds improve with knowledge and skills that come from experience and a willingness to learn. Plenty of people with experience that lack sufficient knowledge or skill.
As a side note, my middle son is a car guy. He recently bought an N54. He has two years of auto service school in his background with ASE entry-level certification exams. We went through his car and I discussed that there are three kinds of work on the car - 1) work to pay someone else to do (way out of his realm/tools/etc) for which I set him up with a very good BMW tech, 2) work that he can do with me and learn the ropes, 3) work he can do on his own. He's executed #1 already, and very happy with the results. On #2 ... valve cover gasket and plugs were done together. We spent about 8-10 hours on that job, and that includes explanation and demonstration which slows things down a fair bit. But my point is not breaking all the shit plastic fasteners on a BMW, getting everything cleaned and prepped, gapping plugs accurately, and doing a job that has an unquestionable result takes time.
Buy a torque wrench ... worth the money!
Filippo
