2001 Volvo S40

it's been having some idle issues, mainly when first start the car i have to give it gas , or when coming to a sudden stop it'll studder a bit.

i recently had both 02 sensors , wiring , sparkplugs , thermostat changed. all original parts.

codes im getting right now are p0172 , p0301-04 so its misifiring in all cylinders.

any ideas on what could be the issue?

 

sounds like your IAC valve is going and possibly a bad fuel regulator on the rail. There are links to fixing these, cleaning these on this site. Im not sure where, do a search.