Did this comp clutch shim removal at the weekend. Easy job... Remove the Nyloc nut shown in the picture you've taken with the caption 'How can I take of this plate' (sic). It's IIRC a 14 or 15mm nut, you'll need a socket to remove it as you can't get a ring spanner it, and you'll need to hold...

That's only 10mpg ish though on LPG, which equates to about 22mpg on petrol... You could see 22mpg running it on jungle juice anyway, so where's the advantage? Unless you have heavy right foot syndrome. Our 98R 4.6 with SPI system returns 18mpg on a run on gas, which equates to nearly 40mpg...