complete tune up, no codes, engine stalls and runs rough on 2002 Nissan Frontier

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
i have a 2002 nissan frontier 4cyl with 90,000 miles. i had the check engine light on for some time but never had any problems. i decided to get a diagnostics instrument. in turn i got the p0400 code, egr emissions malfunction. i didn't pay much attention to it until the truck started idling irraticlly and eventually started stalling. i looked into the EGR system and noticed the a few damaged vacum hoses. to my delight, after changing the hoses and checking the EGR valve(o.k.) the code dissapeared. i also gave the truck a tune up (air and fuel filters, spark plugs and wires, cap and rotor, oil still good.

HELP! now, i have no codes showing up and my truck is still stalling and idling rough. sometimes the engine runs smoother than others but it will always stall eventually.

i'm looking into evap canister, vent control valve, etc. WHY do i have no codes???
(1) Answer