Sr leaning out and misfiring at wide open throttle

[1988montecarloss]

Just got my car running and driving again a month or so ago and it was running just like it always had 11.5-12:1 afr and no breaking up at high rpm but I let it sit for a couple weeks during my final bout trip and tried it out today and was going 16:1+ lean at anything over 3/4 throttle and breaking up after 4-5k rpm

Haven't messed with it again yet as the car is at my parents house 40 min away but trying to get a list of ideas together to test for when I go back to mess with it

So far I plan on checking fuel psi, voltage at fuel pump power and plugs.

Combo is an s13 sr, s14 t28 bb, 550cc injectors, z32 maf, FMIC and enthalpy ecu tuned for the mods. Fuel pump is also hardwired and has been for the last two years so nothing new there