For my '88KRSSE restoration...don't ask...I'm on drugs

Anyway, took it all the way down..had the crank, rods, pistons balanced to .01 of a grm, the heads ported and breathed on, a set of euro cams, Ford injectors, K&N, Staintune, etc;

When it comes on cam around 4K rpm, this engine is smooth as glass,,smother than any of my K75s...and stays smooth all the way to redline.

Which where this question came from...was reving the engine in the garage last night..up to redline, off a little, back up,,,down, up etc. I noticed,...and a neighbor yelled...that I had flames coming out the tailpipe. About 1' of flame each time I rolled off the throttle.

I thought I had everything adjusted for the break in procedure...evidently I missed something important..what could be causing the gas to dump and flame out?