My 5.3 with the LSA blower does the same thing. Only when cold when it has sat for a while. My tuner emailed me several tunes to try and fix it and it never went away. Eventually I gave up and have been just dealing with it as once it warms up it is gone.
I would like to get it fixed. It is kinda annoying.

Maybe its something to do with the LSA map sensor?

BTW I think the lower port should not be caped just open to atmosphere. Upper to vacuum.

 

I agree it is very annoying. And my tuner did the same thing with no luck. Like you said once it's warm it's fine. And I have no idea it could be the sensor but I'm using a cobalt ss sensor.

And I had it vented before I just capped it to see what would happen

 

Whose cathedral-to-square port adapter plates are you guys running?

 

Olson custom works

 

Not that this may help, but I'm waiting on my LSA intake plates to come in, but currently my truck is NA and has the slight stumble issue at idle as well, not in gear so much. Tried bunch of different things in the tune with no luck also

 

I think mine is tune related. I took It to another tuner today and he found a few issues he would correct.

 

Are you stock cam???

 

Yes I am

 

Is Shane tuning this??? Also got any pics of your setup?

 

hes going to be tuning it..i just took it to him for some baselines and to get some issues looked at..after i do my next round of mods hell be retuning it.