Hey there, with any luck you've already sorted this problem-I haven't been online for quite some time so have only just seen your question.
Sydwayz advice is good. Further to this advice, check in particular all "vacuum" hoses for perishing, cracking, poor fit etc. There are a number of rubber vacuum hoses around the intake manifold area such as to the fuel pressure regulator and the PCV hose from the rocker cover to the air intake ducting. Check all the air intake ducting as well.
Any air "leaking" into the system after the air flow meter is not "measured" and the engine therefore runs lean causing surging.