new motor ...trouble starting HELP

[V6 sniper]

I recently had my motor rebuilt and shortly after I had 2000 miles on it, it started taking a long time to start. After about 20 sec. it fires up and runs. It starts right away for the rest of the day, until the next morning, and it wont start again. Also it just started on the highway if i give it too much gas it bogs and backfires. I have no clue what it could be any suggestions

 

[T-top87GN]

Hmmm, kinda sounds like it's having trouble getting the fuel pressure up where it suppossed to be.

Once you get the car started, fuel pressure is pretty slow to leak back into the tank.

Just a thought.

 

[Otto J]

Sounds like the fuel pump reay may be bad, Does it prime when you first turn the key?
There is a safety built in to the system so if the relay fails the oil pressure switch will turn on the fuel pump once adequate oil pressure is present.

 

[2 QK 4 U]

Sounds like MAF sensor

this can cause no fuel and be your backfiring problem.