i have an '89 supra and ive just discovered that it is missing its egr valve and vacuum regulator-as it wont pass smog! ive been to a couple of shops some of which tell me that i just need these two parts, and some that tell me i need a new head! i dont understand this cus i can see the mounting bracket for the egr valve, also all components from the charcoal canister to the vsv are present. i need to know who is lying to me! please help!

It all depends. The EGR system passes through a passage in the back of the head. Depending on the condition of this area you may or may not need a new head.