M135i F20 N55 - Stock vs Aftermarket intake?

[smpeacock94]

Hello all,

I’m new to BimmerPost so forgive me if this question has been answered already. I have a couple of topics I’d like discuss, starting with the title.
I am currently running the Airtec mototsport air intake. I’ve always thought that upgrading your intake was one of the first things you should do when tuning your car. However, upon a little bit of research, I’ve read that supposedly they can actually hinder the performance of the N55 engines. Is anyone able to offer some guidance and explanation for this? I was considering switching back to the stock intake box, but it seems a shame that I spent a fair bit of money on the upgrade.
Another question I have is in regards to spark plugs and the need to go to up-rated ones. I was on OEM plugs, but I was suffering with a misfire so I went ahead and changed them. After a quick look around, I saw that most places recommended using the NGK 97506 SILZKBR8D8S. I’ve had a number of people telling me that these are also unnecessary and I should stick to the OEM and don’t use the one step colder etc. It might be worth noting that I am Stage 2 MHD tuned, with a aftermarket sports car downpipe, up-rated intercooler and of course the air intake. I did upgrade to the Stage 2+ but I seemed to run in to some airflow issues as it was throwing up a code related to “too much air flow” so I assumed this was down to the intake and also increase in power. Some say it’s also because the HPFP upgrade is needed for Stage 2+ but MHD themselves state that it’s not neccesary. My car just didn’t seem to like it.
My final question is to do with general upkeep and maintenance. What sort of things should I be looking at doing? I’ve heard coolant hoses are a good start. Which ones to be exact? Or do I just change the whole lot? Belts and tensioners? I’m currently at 86k and had a service done at Performance M and they’ve advised me that my oil sump gasket is leaking so that needs looking at sooner rather later and they’ve also said I would need to change the “baffle”? Any info on any of the above is much appreciated. Sorry I’m a newbie. Thanks all!