no power under acceleration

[bigchevyc30]

Ok i have a 89 R2500 suburban it has a 350tbi/sm465 motor trans combo. most the time when im going to accelerate it doesnt seem to have much power behind it but there are some time when it shows its true get up and go and is fin but most the time its lack lustered for power. I know its not the clutch slipping as it was just replaced 3 months ago. when it seems to not have any power it wil sometimes pop through the exhaust. the timing on it is set to zero as per factory setting but i dont know what to look for after that. Any help would be greatly appreciated. heres a pic of what it looks like also

[Irish_Alley]

couple questions, does you check engine light come on when you first turn the key "on"? do you have any codes?

[bigchevyc30]

it come on but goes off once started and only code it shows is 12 when doing the blink cde which is basically to tell you its testing right

[Captkaos]

What does the fuel spray look like?  Fuel pressure?  How is the ignition parts?

[bigchevyc30]

not sure about fuel spray or fuel pressure. it has all new fuel pump, dist, coil, icm, plugs and wires. i know it surges when idling.

[Captkaos]

Check your pressure and report.