Aftermarket air filters are a very contentious subject - personally, I've never had a MAF negatively affected by an aftermarket air filter, provided it hasn't been over-oiled.
And also bear in mind that MAFs are generally considered service items... E39 M5 / E46 M3 MAFs tend to start losing the plot between 60-80k km's, while not failing completely, they tend to start skewing airflow readings slightly, hampering performance a bit.
Also advisable on an E36 - check the service history and see what was done and replaced on the car's service record...
For your own peace of mind, do a complete fluid drain on the car - engine oil, coolant, hydraulic brake and clutch fluids, gearbox oil and diff oil, unless you have record of those items having been done at correct intervals. Gearbox and diff oils are notoriously overlooked items outside of motorplan, and can cost you a bundle in mechanical failures that could be prevented by regular fluid changes. Old Hydraulic brake and clutch fluids can cause gunking in the master and slave cylinders, causing premature wear on the pistons and workings, making for expensive replacements / reconditioning repairs.
Also check for O2 sensors, cam position sensors and any evidence of the MAF having been replaced - especially if you find the car running a bit rich / stumbling through the lower rev range / being heavy on fuel.
Lastly, check the front suspension mounts, shock towers, the rear subframe and top shock mounts + surrounding area in the boot.. Unless the car's been owned by a little old lady it's entire life, you stand the chance of some windgat hellcat having been tail happy and over-zealous with donuts and track use, or even just a lot of clutch-sidestepping smoking launches. Ensure the diff carrier / cradle, the surrounding mounting points, and the shock mounts & surrounding body work don't show any signs of cracks or metal fatigue - if they do, get it fixed ASAP, or you'll be in for an expensive repair in future.
Interestingly enough - BMW actually had factory reinforcement kits, containing top mount plates for both the front and rear shock towers, as well as reinforcing plate meant to be welded into the rear towers - though I'm unsure whether they were designed for track use in the Motorsport program, or actually issued as a recall to be fitted to all E36 M3's. Either way though, if you have any evidence of wear and tear in those areas, do as much as you can to cure it and strengthen the area... My old man had a Dakar yellow 4-door a few years ago that'd obviously seen a hard life at the hands of the previous owner, and by the time we caught it, the top shock mounts had practically torn clean out of the body - cost a fortune to fix, and it always made one feel somewhat uncomfortable in really pushing on in the car..
