My 96 454 chevy

I can't say for sure but, Check you're psi that you're fuel pump is puting out. It should be around 55-61 Psi but, you can just call pep boys or auto zone etc.. and ask them to be sure. :)

Btw to check you're fuel pump it requires a spec gauge that cost about 20ish dollars.

Check the oxygen sensors output,

I hope this was of some help. :) If i think of anything else i will be sure to let you know. Good luck

What bank is running lean i would first check for a vacuum leak.