The spark plug manufacturers tell us that +4 plugs should work fine in e36s, but most of us have tried them through the years and have gone back to two electrode plugs, which was what this car came with. I cannot explain why a two electrode plug could possibly work better than a four, but they seem to. I tried four electrode plugs in my old Volvo once, and was less than impressed with them in that car as well.
The e46s came with four electrode plugs, and that is what we use in e46s, which makes this mystery even more inexplicable.
If you have a fresh set of +4s in the car and they seem to work fine, I would use them and get my money's worth if it were my car.