Cobalt SS Network - LNF problem when NLS 1-2. Possibly Spark Plugs? Help plz

Whats up dudes/dudetts,

I have been having this problem lately when i No lift shift. First of all, mods are Dejon Intake, Dejon Charge pipes, Hahn Block Off Plate, Greddy RS BOV, Muffler Delete.

When I NLS from 1-2, and possibly 3-4, i bring 1st to 6k and then pop it real quick into 2nd. I got that part down easy. When it gets into 2nd, the car starts to rumble, lets say when you NLS 1-2, when you get it into to its at 4500 or something. Well it jump down to 4500 when i pop to 2nd and then it kinda holds it there and the car rumbles real bad and makes this weird noise, like brr brr brr brr and then it begins to accelerate. Its like its hesitating bad there for about 2-3 full seconds. It kills 1/4 mile times and i was racing my buddies 2.4 yesterday, i starting spinning 1st, popped to 2nd, got that bog shit, he pulled ahead, and then it finally took off in 2nd and i blew by him. he told me he heard it clearly.

NOW, I thought it was a problem with my tune, some1 told me this happened to them and they leaned out the tune and its fine. They said it was the car running rich on the shift. WELL, i put my stock ECU in today and did another 1-2 NLS witht he stock tune and it happened again, just as bad. It happened so violently im suprised no CEL came on.

What can this be? Bad Spark plugs? Running rich? Intake MAF skews? only happens on the NLS. But since I got tuned I noticed when lightly accelerating sometimes it can kinda rumble and hesitate for a split second. Is this also related? What you guys think?

Side Note: Dont believe its the BOV or Block off plate, after I installed them I NLS'ed perfect for awhile. This has been happening the past months though and seems to have gotten worse and much more frequent over time