I have a code that says im running too lean on bank 1.

What is your question?

I've replaced the MAF sensor and the purge valve and IAT sensor and 2 O2 sensors, and a filler gasket. I've been running premium fuel and checked my vacuum hoses. but my car says I could have vacuum leak, and check fuel pressure. I will be sitting at a stop light and it'll idle at around 700 to 1,000 then just DROP and try and shut off on me. I don't know what else to do. BTW my car is a 1996 V6 Ford Mustang.