[Tonyt915]

Ok, first off here's everything. 2014 328D with 122xxx miles. I've had it since 20k miles and had BMW do every service air/oil/fuel filter change as recommended. At 120k miles I had it tuned by MP with stage 2 tune, Buzzken DP and SCR delete, and AFE intake. Shortly after I noticed when I rolled into the throttle to speed up "not smash the throttle to make it change gears" and let off the car would stumble like it was running out of fuel for maybe a second or less. Usually does it once, every time the cars been turned off and started back up. Thought it may even be the transmission, but yesterday I managed to look down at the RPM when it stumbled "this time a bit more than usual" and saw the tachometer needle coming back up to rpm after the shudder. Called MP tuning to see if it may be something with the tune that needed to be adjusted and his response was the HP fuel pump is going out, cause it should have already gone out with that many miles. Was wanting some other opinions and seeing if any one else has had any issues with any of the above mods? Also there is no CEL coming on when this happens, and usually after it does it once it won't happen again till the car is turned off.

[Hypermile]

I would suspect HPFP if you were feeling sudden flat spot during WOT or hard acceleration. Do you have anything to monitor fuel rail pressure with?

[Tonyt915]

Don't have anything to check fuel pressure. Under full throttle or hard acceleration everything is fine, it's only when I let off the throttle. Usually happens when I'm gradually accelerating then I let off. Accelerates fine, I let off to find a cruise speed and thats when it shudders.

[Tonyt915]

Last weekend I drove some twisty roads for about 2 hours with friends and was really beating on it "probably did 80% of the route flat out on the throttle" . Power was always there with no stumbling. It only does it when roll into the throttle gradually and let off and then reapply less throttle to find a cruising speed. Such as passing a car then going back to the speed limit.

[B58 parts]

This is a reach but it might be the DSC cutting off. Try DSC off mode for a bit and see.

After using DSC off mode exclusively for a month and comfort mode briefly last night I couldn't believe how much it cuts the power down.

[Tonyt915]

I'll try, but it's not like a complete loss of power when you lose traction. It's more of a shudder as if the car was running out of fuel, for less than a second

[Tonyt915]

Also I will note, when it's in sport mode this issue doesn't happen

[Hypermile]

LPFP, fuel filter or transmission is my guess. In sport the transmission holds gears at a higher RPM but in comfort and eco the transmission gears up as soon as possible.

Try comfort mode with manual shift and mimic the rpm and gear of sport mode when it doesn't occur in sport. Duplicate your drive you did in sport but in comfort and use manual mode so you can hold a higher RPM like in sport and let off the throttle and see if it happens. It's all abt process of elimination.

[Tonyt915]

UPDATE:
Unplugged the EGR
Figured it's time to update since it's been 6 days with no symptoms. After trying everyone's suggestions with no luck, I found a post "that I can't find again for some reason" where someone said their car felt like you were repeatedly on and off the accelerator. They described sort of how my car felt when the shudder happened. The remedy for them was to replace the EGR. Wish I could find the post, cause I don't remember why the EGR was suggested. I didn't think to much of it, cause I was under the assumption my EGR was turned off. Saturday a friend came over to help trouble shoot the problem and when he hooked the car up on ITSA. After checking the fuel pressure and injector's, he told me my EGR was still very much active. So we decided to let it close and unplug it to see what happens. I've driven probably a little over 500 miles since then and haven't had the problem come back. Before it was just about every time I turned the car on and off it would happen. Wish I could say why the EGR made it stumble but at least unplugging it, is a solution.

[Enabled]

glad it's solved. Since the tune you have didn't touch EGR behavior maps (like actively requesting closure), disconnecting it is the best choice. Hopefully that valve remains closed.

It was very nice meeting you and your beautiful car.

[Tonyt915]

Was great having you look everything over.

[Hypermile]

Thanks for the update OP!