I had recently bought an 04 G35 Sedan and I’ve fixed a bunch of issues, had a new coil pack burn up and blow a fuse but there was 2 extra fuses under the dash and when I removed them and started up the car there was white smoke from the exhaust I put them back in and the smoke had went away, I haven’t been able to find anything about this issue online

 

The spare fuse slots are both stacked on one end. Those were the ones you removed yes? Try removing the spares again while it's running. Those slots should be completely depinned from the Fuse Block - J/B however it's possible a previous owner pinned them and was using them to control something aftermarket.

Look into the slot when you remove it and see if someone added pins, they SHOULD be empty.