I would agree with most of that.

I used K&N air filters on fast road and rally cars for years. The main advantage was being able to do away with the airbox and being able to clean them between events (especially dusty stage rallys in the summer).

I have a Maptun, oiled filter in the airbox on my Saab Aero. it may have liberated a mouse power or two, but the big advantage is that it can be cleaned rather than replaced, so by the time I've had the car 12 years or so it'll have worked out cheaper. It is worthy of note that the standard air filter for my Saab has a steel 'mesh' behind the element with holes for the air to pass through - the Maptun does not and so should yield some small improvement.

As you say, power increases will only come by modifying or scrapping restrictive air intakes (I've removed the stupid swan neck thing from my Saab). But this will result in an increase in intake noise in most cases.

I think that if you read K&Ns marketing material very carefully, they don't actually make any 'wild' claims, but the wording is very "persuasive".

For their oil filters, they do make some specific performance claims with regard to particle size that can be trapped etc. But as I no longer work in auto R&D I cannot check their claims against OE specs. They do, however, "seem" to be claiming that their filters are better than OE requirements for particle entrapment and flow. Although M&H are an excellent brand, I am currently persuaded by the evidence of my own eyes that it is their filter that has been rebranded as K&N and as such think it is disengenuous of K&N. You can't blame H&M for selling their (excellent) product to them.

I get M&H filters as well as other good quality aftermarket service parts from my local factors, never get a moments problem with them.

Found out a long time ago that not filters as with other parts are not all equal, some time spent trying to prime a new Diesel fuel filter had me removing it only to find the area around the seal was badly stamped, this was one of the usual accessory shop dross brands.

OE is obviously the best choice but some main dealers have made their parts dept something of a chore these days to say the least, can't be bothered spending 20 minutes whilst they make a mountain out of a molehill....bring back the proper dedicated parts dept with a knowedgeable storeman in a dark blue smock behind a huge robust counter who knew most of the parts off by heart and which parts could be interchanged or overhauled/rebuilt...i get the feeling some makes and dealers would prefer to do away with a publicly available parts dept altogether, thats fine won't be darkening your doorstep again.

I buy OE Toyota filters on ebay from a Toyota dealer.

Cheaper, much more coneneenient and saves a 20 mile round trip to our local dealer.

No brainer.