1980 LS bone stock

Car runs great. If you try to drive it befor fully warmed up or low on gas it kidna shakes wen you take off and wont accel and back fires.

So what I did inspected evrything. Changed oil and fuel filter notice some rust flakes out of filter when I tilted it upside down. The fuel lines on carb were leaking bad washers fixed that. Ignition module went bad and coil fixed that.

"same day I buy the car"

So now I drive shift at 4k or so in first to 2nd get on it hard pulls right on up but at 5.5k through 6.3 high as I brought it so far it sputters bad and has no more will to accell. Shift up and pulls right back up to the point.

I go to waffle house eat get out start car. Sit 3 min 4 min take off get on highway roll on the gas and sputter sputter back fire back fire push in the clutch to hold any momentum I had and cost into parking lot. Put it in 2nd car takes off perfect no more issues.

Girl is driving the car now. Runing fine pulls out of a suicide lane to cross traffic in 1st car fully warm and it sputers onto its face and back fires back fires. She pushes in clutch coasts trys it again car is fine.

The back fires are coming out of the after burner pipe. The small pipe runing along side the normal exhaust flow unmuffled. actualy I have never seen these befor nor had I seen a SA befor but my uncles FB without a fully stock exhaust was lacking this. My dad told me what it was.

Any help I kinda feel like

 

well, your fuel filter is likely plugged (common issue)
its located under the car, fore of the driver rear tire.

the flame shots out the "After burner" pipe are mostly normal.. this pipe should be fed by the air pump, which your BONE STOCK car should still have installed. if not, and you dont have cats (im not aware if you do or not) just plug it up, pich it closed, or buy a racing beat full exaust.
otherwise, attach the air pump again.

 

Just changed the filter as I said unless it pluged again.

Yes cats pump evrything mint 70k car

 

hmm.. if that hose isnt connected like you say, then the cat may be carbon fouled.. this happened to me.. the previous owner drove it around with the air injection hose dragging for months.. when i opened up the kitty i found a solid brick of carbon. i hollowed it and damn near shat myself at the difference.

 

Hmm I was going to bet the cat was clogged but most cars I have drove with one just had no power anywhere. I will take it apart.