2002 Mazda Truck P1537

I failed smog, P1537. Aamco wants 400.00 to replace intake manifold runner, I replaced the IAC valve and my check engine light went out but after I restarted it, it came back on. Is there anything else I can do without taking it to aamco? They also wanted 95.00 to replace the switch on the brake cause it wouldn't come out of park after the truck was started more than 2 seconds, but I replaced it myself for 8.99 today and it still didn't work, then I noticed that the 7.5 fuse was missing and replaced that and it worked, so they were going to get me on that one. So now I don't trust them.