spark plugs are not a modification or anything, use the original spec. their sole function in life is to ignite the fuel mixture in the combustion chamber without other errors like melting, pre-ignition etc.
For the MAF and throttle problem - it is recommened to clean the MAF only with 80 or 90% isopropyl alcohol - I usually dunk the whole thing in it for about 2 hours and let it air dry for another 2 hours. The throttle is best left alone. And yes you need the air filter box clip, it can create big problems for you like resonance in the box, dust in the engine etc. for the time being use a temporary tiny C clamp or a cable tie.