Missing when cold.

OK background:

Dallas Tx.
2000 Chevy 1 ton - 5.7 350

About 130,000 miles

New sparkplug wires
Fairly new plugs (6 months)
New Cap & Rotor
Clean K&N air filter
One of those computer upload upgraders running 87 octane and programed to 87 octane.
Cleaned throttle body with cleaner and temp sensor in intake.
No Codes
EGR - 2 years old
Fuel Filter - 2 years old
Cleaned Fuel injectors about a year ago.

Starts right up and idles great.

When the engine is cold, if I bearly push on the gas to drive it, it seems to miss and backfire a little.

If I push down on the gas a little bit harder it does not miss or backfire.

Once the truck warms up it drives fine which takes about 20 miles.

But sometimes when I am bearly touching the gas pedal around 60 mph is seems to miss a little.

Any idea why it is misses and backfiring like that?

Thanks in advance.

Some owners of 2000 C/K trucks with 5.7L (RPO L31 and VIN Code R) engine, may experience a Service Engine Soon light, misfire, rough idle or hard start due to a deposit build up on the Sequential Central Port Injector (SCPI) poppet valve(s). The deposit build up may cause injector poppets to stick closed.

Regular cleaning of injectors will not work on this system..there is a specific procedure (if you do a search, I have listed the procedure many times before) for this injection system.
There is also a upgrade injection unit available thru GM parts for this.

Some owners of 2000 C/K trucks with 5.7L (RPO L31 and VIN Code R) engine, may experience a Service Engine Soon light, misfire, rough idle or hard start due to a deposit build up on the Sequential Central Port Injector (SCPI) poppet valve(s). The deposit build up may cause injector poppets to stick closed.

Regular cleaning of injectors will not work on this system..there is a specific procedure (if you do a search, I have listed the procedure many times before) for this injection system.
There is also a upgrade injection unit available thru GM parts for this.

Thank you sir !