I did a search but perhaps didn't stumble across the correct search term.

Any, I bought a 2005 Mini Cooper S manual with 138,000 miles in pretty good shape. 17? pulley, cold air intake, aftermarket ignition, OEM ECU software.

Although the engine feels strong, it has a consistent stumble around 2,800 rpm. My read on the engine is that, although it's not yet in it's power band, there should be no reason for the hesitation/stumble when accelerating through 2,8000.

What might be the problem? What fix, if any?

Thanks.

 

Mine used to do that, I changed the spark plug wires and that fixed it. You might also consider the spark plugs and maybe the coil pack if those don't fix it.

 

I have the same issue with my 2004 mcs from about 2800 rpm to 3600 rpm. More noticeable in 1st to 3d gear. Also only feel it when vehicle is under load. Weird thing is that I don't feel it when vehicle is on neutral and I rev the engine. Feels like the car is going and hesitating very quickly. I think u may be referring to the dreaded " yo-yo" feel that seemed to be more prominent with the pre-facelift cars if I'm not mistaken.
it has definetely become much more noticeable wih my mods and especially now with a cam swap.

Some guys had the detroit tuned by-pass valve mod and it seemed to help. in my case it made it worst.

Not sure what the issue is, but to me it is feeling like on my car its fueling issue perhaps or even ems2000 ecu issue. Not sure ....

 

Any engine codes popping up indicating misfire or anything on any particular cylinder? Alot of times one of the terminals on the coil pack understeer boot corrodes , that's worth checking. If you think it's your coil and or wires too I got stock coil and wires if you'd need them( are very low miles) , just shoot me a price and I could ship them wgen ever...
but adding parts to correct an issue is just covering it , find and address the issue.. a stumble is yoyo. Yoyo only happens while in 1st gear cruising slowly so that's not it. Sounds like your experiencing a miss under load so either ignition or intake related. Do you have a boost gauge ? If so should be at around 16ish max psi and at idle minimum of 13vacuum.