I have the same problem.
Engine B16A2
Mods done to it:
ek9 pistons
ek9 cams
supertech valves
dual valve springs
skunk2 intake
oem TB
hyteh header
The thing is when it's very cold in the morning, the car starts but when i touch the gas it chokes out. when i start it again in idles roughly like a v8 and i can smell the gas. But when i start the car over the day, it works fine. I bought the swap from a friend and he sais the engine was working perfectly. But when i put it in my car i realized there were some things done badly. Like the FPR had only one bolt in it. When i fixed that the engine started acting wierd.
when gently accelerating betwen 2k%3k RPM the car twiches. Like its loosing power. And when it goes over 3k rpm it works fine.
Things that were changed
New O2 sensor
New TPS
MAP sensor
IACV
cleaned TB
New vacum lines
new spark plugs
new ngk spark plug wires
new distributor cap
new FPR
Any ideas what could it be? Is it posible it's badly tuned?
What fuel pressure are you running? How old is the fuel pump?
After that I would look at your injectors to be sure they are clean and working properly, duty cycles.
I have exactly the same problem on my car ... When the weather is cold (under 5°C), I start it and it stays around 12.5 - 13 AFR but when you touch the throttle it goes 10.5 AFR or less and dies.
Then when you start again it runs like a V8 for few second at 10.5 AFR and it rises to 12.5 - 13 AFR again within 10-15 sec
I always have to let it run at idle for at least 1min.
Problem comes from my ECT and IAT correction advanced tables on ECtune. I searched on ECtune forum and many users encounter same issue. In most cases ECT + IAT tuning solves the problem but in some cases it doesn't work. For second case, the solution is to use a second table for cold start to avoid the problem ... not the best solution but it seems to work and even Calvin tested it and confirmed that it works.