OK so I am 100% going to do a 3400 swap, and I want to know what is the easiest wiring pcm setup for a 99 cavalier. I know 2000+ you use malibu setup, what about 99? My best idea so far is to use a 2nd gen z24 3.1 pcm and harness and my pcm. Only one question, would I need to piggyback after that for gauges? Any other possible easier routes? And what all would I need for the 3.1 gen 2?

You're better off to use a 98+ Grand Am 3400 PCM for the engine than the 2nd Gen 3.1 PCM. You can use HPT on it instead of en emulator or burning a chip, and it's no less compatible for piggy-backing than the 2nd Gen PCM. However, I would put a delay circuit on the ignition power to the J-body PCM so that it comes on a few seconds after the 3400 PCM, to avoid the issue that someone was having with the odometer ticking up every time the car was turned on (some pulsing between the two PCMs was likely responsible for this, so by having the piggybacked PCM come on after a delay should eliminate this).