[AS4EX]

I noticed when pulling through the gears, there is a hesitation around 5-7,000rpms. It's almost what I would describe as a split second 'hiccup' or a "chug", and power is interrupted but as I said, returned in less than half a second. However, it is enough to physically feel for that split second. My theories despite what the service interval is on the OBD, possibly new plugs, the dealer filled it with crummy petrol, maybe oil, but dubious. Any other ideas what could be the culprit to check on?

[unrealii]

My 96 ford taurus used to do this between 3500-4000 rpm. It ended up being a faulty camshaft position sensor

[smallseafishie]

My car did that when the plugs were due. It eventually does throw a CEL.

From what I've gathered here, the big 3 are plugs / injectors / coils for that symptom.

[SAM67]

I would add carbon build-up on the intake valves to the list. I experienced a hesitation while accelerating in 4th-6th gear (6spd manual) between 2,000-3,000 RPM with no codes thrown. Car had 45,000 miles at the time. Walnut blast was (eventually) done by the dealer under warranty and it fixed the problem. OP's issue is at a much higher RPM but it otherwise sounds similar.

A year later at 55,000 miles I started to experience a similar hesitation/miss around 2,500 RPM in all gears while under load. Dealership first recommended clutch replacment but I declined. Instead, I replaced the spark plugs and the hesitation issue nearly disappeared, for a while at least. After several months, I finally got a check engine soon warning and the car is now running really rough on cold start-up but no long cranks. Codes indicate mis-fires in several cylinders. I suggested HPFP (since it's covered by extended warranty) but dealership now believes it is the fuel injectors. I have an appointment to replace all 6 injectors with the latest re-designed version. Not cheap. Very disappointed that fuel injectors are not covered by an extended warranty since they are one of several known "weak links" with the N54 engine, including HPFP and turbo waste gates. It's worth noting that all 6 injectors were previously replaced under warranty at 27,000 miles. Love the car when it's running well but it's definitely had it's fair share of issues.

Good luck OP.

[idrift4wd]

Ever heard of something called a misfire?

[AS4EX]

It's actually one of the first things that came to mind. Just turning here to see what a few others would say before I start spending. Are there some other stores to check out for maintenance items other than ECS or getbmwparts?

[El Cheapo Loco]

Buddy's 335i has the same issue, slight hesitation at WOT. Dealer changed plugs, coils, injectors to no avail. Intake valve cleaning did the trick.

[AS4EX]

Do you have an idea what it cost him for the job?

[El Cheapo Loco]

It was under warranty. I've read here it costs somewhere from $400 to $600. Just don't do it at the dealers.