[Arexander]

Hello everyone,

My car:
2008 335i
N54 motor
33,xxx miles

Mods:
K&N air filter
Cyba scoops

Long story short, I had a Cobb AP v2 on my car since January of this year. In February, I started blending e85 (30%) + 91 octane (70%).
Around that time, I put my car on the Cobb's Agressive Stage 1 map, and car started to drive horribly. I took it to dealer, and one of the coils had gone out.

Recently, I had set it again to Aggressive mode thinking that the coils were all good. And about 4 weeks ago, it was driving fine. Until I gunned it, and a CEL code went off. I drove it on the freeway for about 20min. Parked the car, light went away, but to not take chances, I un-installed the Cobb.
I sold the Cobb AP to another member 2 weeks ago. The car was running fine and no error light.

And about a week ago, I went to the gas station, put in the 30% e85. However, there was such a long line for the 91 octane pump, that I told myself I would just fill up after work. When I left work the light came on--"Service Engine soon."
I put in the rest of the 91 octane, but the light didn't go away.
Then, I took a friend's advice by unplugging the battery for 15min., but the light still didn't go away.
Then, I waited until the gas was a little past the reserve on Empty. I refueled with 91 octane on a full tank, and the light is STILL there.

So, I took it to a local oil shop, and the p0171 & p0174 codes came up.

I have been doing research and it seems that the majority of the issues boil down to 2 possibilities:

1. Vacuum leak
--I did have an ER cp a while ago, but went back to stock.

2. Coils/Plugs
--Could it be that I should change them all, even though my car's mileage is really low?

Any advice from you guys would greatly help. Thanks so much.