high idle, check engine light 84 trans am

[1982firebirdSE]

Hey all, i have a high idle on this 84 trans am, with check engine light illuminated.

It also drives fine under light throttle, but under more than 40% throttle, the car feels like it is holding back, like it is starved for fuel, or bad ignition, and it nearly full throttle, it starts to surge and get rough.

After driving it for a while, i switched it off, and 2 seconds after turn off, the car let off a backfire!>!@>!

The 305 was swapped for a new 350 goodwrench 4 years ago, but all origional wiring, etc has been put back in place as per factory.

Any suggestions??

Thank, Mick.

[TAdan]

What kind of carb are you running? Has it been rebuilt?

Have you checked what code the check engine light is giving you?

[1982firebirdSE]

carbie is the factory one for the car, it has been rebuilt.

I have not been able to get a code as yet.

[1982firebirdSE]

had a mate go over the car for me, looks like the carb may have not been built, but, dont the quadrajet's have flaps that open with air vaccumn as throttle opens more?

Under light throttle it is fine, but under hard throttle, it cant/wont go....