Fury3

Hi, I'm new on the site. I've been in Georgia since '92 and enjoy it here. Like most on the site, I have been playing with cars, trucks, etc for years. I have more old school experience than the computerized, fly by wire stuff.
I've just been through a rebuild on my 2003 Silverado Z71. It has the 5.3 VIN T motor. I was looking for bulletproof with enough power to light up a smile but still get reasonable road mileage with towing capability.
Had the bores cleaned up, added, pistons with coated skirts, comp cams XR259HR cam, upgraded rollers, Gibson headers, Flowmaster hi-flow cats, magnaflow muffler. Also got a Diablo In-Tune. Still on initial miles before downloading tune and then sending data off to Diablew for the custom tune. Having an issue with P0300 intermittent misfire DTC. The engine is solid and done right (no time & used a great mechanic) so I am thinking I may just have an ECM or sensor that isn't liking the stack of cold air FIPK, cam, headers, cats, etc. I am thinking a crank position relearn and then tune and off for mapping may be the solution.
Does anyone have any experience with this or feedback? Thanks