I suggest you get the 550 tuned up and sell it. You clearly have some concerns / issues with it providing what you need. So, sell it and put the cash toward something that will actually give you the performance and function that you need.
I laugh every time I read threads about people that buy a sled for some sort of "bargain basement" price and then look to dump a stackload of cash into performance parts. BUY THE SLED YOU NEED in the first place.