96 Tbird intermittent starting problems

Last summer whenever it was 80 - 90 degrees outside the car would sometimes not start right away after turning it off. Or it would run for a minute and then conk out. Ignition would turn very fast but seemed like there was no fuel. Someone told me it was vapor lock and the best I could do was let the car sit for a short time to cool down. Now it's only in the 30's and once in a while the car does the same thing. After shutting it off it starts and runs ok then conks out if I have to take my foot off the gas right away(such as backing up or stopping for a stop sign in a parking lot) and I have to let it sit. It doesn't happen very often, just enough to irritate me and other drivers! What is it and is it expensive to fix?