94 k1500 surging idle

this is really confusing i check for codes and there are none present timing is set at 0 ive changed fuel filter and air filter and pcv valve im at a loss to where to look please help

Check the idle air control valve, in the TBI unit. It may be sticking
or plugged. The hose from the TBI to the pVC valve can split,
or the power brake booster can cause idle problems too.

if its an automatic try unplugging the torque converter lockup.. its a blue 4 wire connector that plugs into the tranny