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I was looking at my tyranid army on battlescribe and it says impaler cannons dont have haywire rule anymore? Is battle scribe correct?

Never trust battlescribe (or any army builder). They aren't offcial sources of the rules.

What does the actual codex say?

Impaler Cannons were never Haywire.
The Hive Guard have access to the Shockcannon, which is a Haywire Blast.