i have a 430 mast MCS 25/IMCS 21,48 mast extension and a 150 boom,my board is 93L what is the biggest sail i can use

i use a 6.6 on my 93 (90kg) and i wouldnt want to go any bigger

For that mast size you would be looking at a 6.3 - 6.5 or so depending on brand.

However you will almost certainly need a boom that will go up to 180 or thereabouts -- is the 150 you mention as your boom size the min or max length?

yea the boom is 150 min