S54 power loss at 6k RPMs

[happyhotdog]

Hello, I purchased my first M car (2008 Z4M) about a month ago. While I love the car so far, it's having some power loss around 6K RPMs. I noticed this while driving, and I took it to a dyno around town and the results affirmed my suspicions.

It appears to drive perfectly fine up until around 6K, where it just feels like it's giving up. There are no strange noises, or anything else. Unfortunately, I'm not able to post attachments, but the dyno results show that it dips about 25 WHP between 6-7K.

250@6K->225@6.5K->250@7K

The only modifications I'm aware of are Fabspeed headers. Current OBD codes are catalytic converter codes, which is presumed to be from the headers deleting the cats. The only thing I've done since the dyno results is replace the spark plugs, but it still feels like it hasn't fixed the issue.

I'm hoping someone here can give me some advice on what I should do next. Any help is appreciated. Thank you!

[shreyasvraju]

It's def strange that there is a dip in the curve.
1. Does it have stock intake?
2. You sure it doesn't have a tune on it?