I have an 88 GT with the Trickflow top end on it. It runs hard all the way through the RPMs while is cool...but after it heats up it spits and sputters around 4500 RPMs and throws a "lean" code. I had this car while I was stationed in California so I had cats on it the last time it was tuned. Since then, I've left the Communist Republic of California....I have long tubes into some flowmasters now. Anyway, the only thing I can think of is a bad tune. What is the best way to get a new ECM that's tuned correctly?