Car Setup
Boosted 2013 Civic Si
I have a full Maxspeed kit, RBC, including a new 6262 turbo, Stage 4 Action clutch (unsprung) with a lightweight flywheel, and a rebuilt Gear X transmission. The car was already boosted before the transmission blew, and it was running perfectly with no issues. After blowing the transmission and upgrading the clutch, turbo, and transmission, I started experiencing a really bad sputtering issue.

Symptoms:

• The car bogs badly on cold starts. The idle fluctuates up and down before stabilizing, and it backfires during the cold start idle.
  
• While driving in this temperature range, the car backfires heavily and sputters.
  
• Excessive backfiring with pops and bangs occurs during deceleration or when feathering the throttle.
  
• The car backfires and feels off when shifting gears.
  
• When downshifting to second gear, the car bogs as if fuel is being cut off and then suddenly restored.
  

Additional Info:

• No CEL codes are present, though I do get a P0128 in the morning, but I don't believe it's related to the issue but i could be wrong.
• The VCT has been cleaned after noticing the cam and command weren’t hitting their target.
• The injectors have been cleaned, and no issues were found with them.

I have contacted my tuner and he is a very reputable tuner, and we have been over couple logs trying to figure out what the problem is. I do have datalogs that i can send also.