best food for max pleco growth rates

depends on the species, but i'd go for a balanced diet.

a few key ingredients off the top of my head
1) Bogwood. i put it in regardless of the pleco species, and it helps the water quality to suit the pleco. Helps with roughage and digestion, the lignin, and creates the softer slightly acidic water.
2) shelled peas- these are fantasticly full of vegetable based minerals and vitamens, as opposed to cucumber and zucchini. I also believe water lettuce to be very good.
3) again for vegetarians- roughage is a must to keep there digestive tracts working. best for this is probably potatoe aswell as cucumber, zucchini, parsnip.
4) The bright colours- this is in meaty foods to help keep them very colourful, and all plecos should have it in their diet to keep it balanced. Also vegetables that contain natural "dyes" such as carrots can also have an affect. (dont expect an orange common pleco or anything though)
5) The meats. carnivorous small plecos in my experience should never turn down bloodworms, live or frozen. it is fantastic for the smaller plecs as they can eat it, and grow quick. i have to saw experiment with the prawns you give larger plecos and see what effect that has.

A few things missed are fruits and commercial foods

That is a tough call. You are asking which food is best for all the plecos? haha you know better. There are too many.

For commons just throw them in a tank with algae growing on the sides, they grow from 2" to 1' overnight.

For herbivores, bog/driftwood, and if you want to go high tech, blend 1cup peas, 1 cup zucchini, 1/2 a kiwi, 2 market shrimp. Puree them up, place them in a ziplock, flaten, freeze. Great to get your royals growing very quickly.

Carnivores... meat. Shrimp I find to be the best, due to its ease of use, and availability. Very good growth, and stunning colors.