.... the replacement air filter is a cheap one by Crosland which is not the Crosland of old. These are now made in India. The other filters are ok being made by Mann (Oil) and Bosch (Fuel). The thing is I now want to change the air filter for either a genuine Toyota part or a decent aftermarket item. Any thoughts anyone?
If you had your cruiser's details in the sign-line, I wouldn't have to search to find out which vehicle you are referring to...
Anyhow, found out you have a 2001 HDJ100. This probably means that you air filter is of the cyclone type, with a filter that you don't change, but clean. The original filter has a huge surface area and filters down to very small particles, can't remember the size in microns. When you do an oil change (e.g.) you blow out the filter and put it back in. If it looks dirty, or every 20 k miles, you wash it in clean water as well. If you are going to drive right away, you just shake it and put it in right away, and the airflow will dry it out in no time. If not driving, leave it out to dry, to prevent corrosion. There is no other filter that can replace it. It will last a few 100 k miles. Change it if it corrodes too much, or if the fabric starts fraying.
For the oil filter, according to all tests I've read, and after cutting open filters, there is no other filter with the same features as the original, which filters both the main flow and the by-pass flow as well as the oem. While another filter can do a good enough job, I can't see why you would want to use non-oem. The price difference isn't that big, and definitely not worth it if you want to keep the car "forever". There is normally a difference in mark-up, so that the shop will make more on selling a pattern part to you.
For the fuel filter there is less complexity, just compare the filtration, flow and the surface area. There is a problem on the 100 tho', with the low "ceiling" of the filter holder, where there are a few filters that do not have a low enough top surface to give a free flow. Like a 80-series fuel filter can give a restricted flow if you mount it on a 100. According to what I've seen, there is no other filter with the same size of the filtration area, but that doesn't necessarily matter if you change filters often enough. (Especially with clean fuel straight from the pump)