Help..BMW E28 Air Filter Upgrade!

[e28 boy]

i had a BMW e28 and i plan to upgrade a Simota Cone air filter, but i'm not sure about the diameter of the front adapter ( which connects to the steel air filter box ) because my car is in another state. Can anyone post the diameter of the adapter? So i can buy a preferrable neck size ( i think the E28 AFM is same size as E34 AFM )

I had a few questions here:
1. Will it increase the horsepower and torque of my e28?
2. Do i have to adjust the AFM after i install the simota air filter?
3. Does more air flow damages the engine?
4. Is it worth buying one, or i just stick to my traditional box-style OEM air filter, because i haven't change it for years..?

Sorry for asking many question, but i really need you guys help here...

Thank you.

[bimmerd00d]

Usually a good filter in the stock airbox is good enough. I dont know much about the E28, but in the E34 a cone filter makes it sound cooler but no real increase in hp. No need to adjust teh AFM. Change that stock filter to a brand new stock one, dont get a K&N.