Tahoe tachometer freaking out.

[StevenDey92]

Just had my hoe in the shop for a good week. She was dying intermittently while driving. After a good 10 hours of diagnostics they finally figured out what was going on. Injector 1 wire that connects into PCM was loose. Haven't had it die on me yet. Knock on wood. But now the tach freaks out. It idles just fine in neutral, but as soon as I put it in reverse or drive the tach goes crazy and she runs terrible. And then when I give it some gas she runs just fine. Driving and coming to a stop light, she idles just fine in gear. Can anybody help me figure this out? Thanks. Here is a link to a video I made.

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