Any ideas on how to greatly increase my profits for my lunch truck business? I cant seem to get it going?

Hire a new chef.

I looked into that business once, the start up costs and commissary requirements are daunting.

Menu, price, and most importantly locations to sell to.
Permits and permission to sell on premise are also hurdles to deal with.

Keep it simple, don't spend money on items that don't sell, variety isn't usually a big thing, good food is.

Service, hit less places and give more targeted service to the locations you go to.

Work out special agreements with companies and their employees as to what you offer, when you offer it and discounts for large or in advance orders.

Promotion is an expense, but try to keep it targeted and local and do it yourself, projecting a more personal touch other than just the "lunch truck guy/girl."

Schedule your itinerary of stops to maximize how many places you can serve to and how long you can stay at each one.
Get to know the names of your regular clients and their likes and don't hesitate to suggest items you might think they would like to try.

I'm sure you probably know or have done most of these, but at least it can be a check list to help you narrow down your strategy.
good luck.

btw, if you get that nursing degree, you can also offer health care for indigestion, heartburn, Heimlich thrusts, CPR, blood pressure screening, etc. sort of a one stop shop,
you will blow the competition away.......Hey, could work.

get a liquor license

It's simple to attract customers by lowering prices - but that's only a good strategy if you can do huge volumes. It's better to make your offerings more appealing by offering more, not by charging less.

With food, it helps if you offer something they can't easily do for themselves. They can make egg salad sandwiches at home and brownbag it - and in this economy, they're likely to do exactly that.

I'd be inclined to focus on barbecue. To make good barbecue, the stuff has to be cooked low and slow - and people don't have the time (or the smoker) to do that themselves. Barbecue doesn't have to be messy; you can offer pulled pig sandwiches, for instance, instead of ribs by the slab. You're using very cheap cuts of meat, which keeps your costs down.

Hot dough is also cheap to produce, but highly appealing. Think cake donuts, or soft pretzels (NOT Hot Sam type crap, but stuff like Auntie Anne, with toppings like cinnamon-sugar, or parmesan cheese, etc.)

The three big factors in any retail business: location, location, location - and you can easily change that. If you're parking by a factory that has a lot of laid-off workers, not only are there fewer potential customers, but the remaining ones are worried, and tight-fisted. Park where there is more prosperity, and you'll do better.