Not Running Right

This may be a long post...I bought this car back in November late. It had an issue of not wanting to idle below 1500-2000 well they took it in the shop and it ran good for a day then back to what it was doing before. took it back and they sent it out to a tuner well about all I got to do was drive it home..about 70 miles and put it away because of the weather. Got it out this last weekend it continualy wants to idle at about 1800 but when it isnt doing that it does this 1000 rpm down to 200 rpm thing sounds like it is stalling out but recovers.this is a 2004 it has a cam ( not sure what size but pretty big.Heads and lg headers and ligenfetlter intake. Any ideas would help..Tuner says its just the nature of the beast I aint buyin that...Thanks in advance for any help