plastic? Erm, no, they're alloy. Explorers and LPG are a good combo.
As for your std 58mm MAF, this will be the new choke point in your setup, source a larger unit. The el-cheapo way of getting more flow through your MAF is getting an AU MAF housing and plugging your ED's sensor into it. This isn't ideal as the tune won't be calibrated/mapped as you're creating a FrankenMAF, however I've done this and the EB doesn't seem to be complaining. I noticed that after 2500rpm it revs a little more quickly towards the redline, however it is a bit lean in the midrange.
I'm not too familiar with what is out there with regard to aftermarket MAFs, but maybe try
www.fordforums.com.au or
Ford Modifications Website - www.fordmods.com and ask in the appropriate sections there.
Cheers
-Dave-
