huge idle/dying issue

[69camarokid]

So the engine is a 95 trans am LT1 with T56 with some mild modifications in my 69 camaro. IT is still fuel injected.

WEll yesterday my gf and i decided to go to raging waters, a water park about 35 miles from my house. Gorgeous day so I decide to take the camaro. The car runs flawless on the freeway, but a few minutes after exiting the freeway the car starts to have issues. While sitting at a light the idle starts to get erratic. I tried to give it gas, but it had little to no effect on the engine.

When i tried to take off, no matter how much gas i gave her, she jumped all around like a kid learning to drive stick for the first time, then she died and refused to restart. I checked the temp and it was a solid 190, no issues there. After about 5 - 10 minutes she started up and gave me the same issue of jumping around through third gear, after third, as i got back on the freeway she ran fine again.

THis happened a few more times i would get off the freeway and have to come to a stop. Sometimes it would happen, other times not.

Im wondering if this could perhaps be a fuel flow issue, because when i drive the car around day to day on the street i never really have this issue, its only after hiogh speed freeway runs.

any ideas would be great, thanks