96 Yukon. New Motor. Dies on deceleration

[voyantus]

Hi all. I have a 96 Yukon. Recently replaced the engine with a crate motor. Shortly after, it began dying on deceleration (off ramps etc). Starts right back up fine and idles fine then. ALso doesn't die if you only drive slow and never get the RPM up. I'm stumped and so is the shop that did the work. Just thought I might throw it out and see if anyone has any insight. Thanks.

[SunlitComet]

:welcome: what about codes?

[retorq]

Mine does that ever since I put in the new fuel pump. I had to hack apart the "bucket" and when it's low (under 1/4) going around corners or stopping quickly will do that.