I try unplugging both starter and alternator power(+) wires and then plug in the negative battery wire and still sparks like crazy.

Update: unplug all engine plugs (isc, tps, maf, etc.) And still does the same. Seems like the two white wires from the fuse box is short? But, why?

You got a dead short some where where you connect the negative, the short is causing the sparking due to the sudden load.

Got some checking to do with your wiring system.

As for the one ground connection you mentioned: I'd do the intake to negative post on the battery, not to firewall connection - might cause a ground loop doing that..and this could be causing your problem. Grounds are a terribly grumpy element - have to be treated right.

You mean I should try to ground all my ground wires back to the battery? I'm leaning more towards a shortage somewhere more than a bad ground.

A) battery to tranny
B) battery to fire wall
C) intake manifold to fire(the smaller wire)

Let me if I'm missing a ground or should change something.

All ground wires should be the same wire gauge.
Don't use smaller gauge to use as a ground wire.
That's a lot of current flowing from the battery ... and DC current flows negative to positive-why it's super important to have all ground connections rock tight..have the ground strap connected between exhaust pipe and chassis due to the exhaust pipe is floated by rubber grommets and not grounded.

But, true : Check for shorts in the electrical circuitry-might be an audio device still directly connected or similar.

Good luck - DSM

This thread reminds me of starter cables being switched. Just a feeling.
http://www.dsmtuners.com/threads/stupid-starter-wiring-question.443067/

Agree .. makes one wonder, esp when cables have been replaced and no color was used to define polarity...and where this OP mentions of decent sparking when connector being removed or attached.

Granted, not familiar how batteries are in place with 2G setups, but with 1G, the negative is closest to the firewall with posts facing the INT manifold. Thus, the Positive cable would have the MPI fuse and other fuses attached to the positive connector along with the starter cable.

EDIT: That was quite the read from that link that was posted.

Then, the OP, of this link, mentions on getting another starter ... and hope he got the right one for the transmission in use.

Thanks for the link and feedbacks. Now I know forsure that my starter is hook up correctly. The positive (red) wire is hook up in back of the starter post closes to the firewall. Stater clip Is plug in. No wiring touching each other. And "starter" ground wire is connected to the bellhousing and negative cables(neg post on battery) .

I eventually found out we were testing for the shortage wrong the whole time. I think I found my issue with major sparks when trying to plug in the negative cable to the neg post on the battery. But, I still have to hook up the rest of the engine wiring(tps, coil, maf, etc) to confirm my problem is solve. Ran out of time today.

I'll Let you know the results tomorrow or when I'm finish hooking up all my wiring.

We did eventually figure it out. It seems like the alternator was shot. Took the alternator out and had it tested at autozone and it fail. Therefore I got a new alternator and slap it on and "wow-la" problem fix. No more sparks when trying to plug in the neg. cable to battery.

Interesting. Normally the fuse pops (alt is protected) unless you're super quick with the battery cables and not blow the fuse.

The one white wire lead coming from the battery connector runs to the back attachment post on the alternator.
The field winding attached to a rectifier inside the casing, needs the 12v feed from the battery to operate, which is switched from the key.

Prob the rectifier had shorted across causing the spark when attaching the negative connector where it was on all the time. Thus, this was being away from the 80A fuse why this fuse didn't pop.

If you want to see how your charging system is doing, using a VOM, you touch the post with the RED positive lead and ground with the black lead with the motor on idle.
Output coming from that red lead should be in the range of 13.8 to 14.3 volts.

Glad you found your problem. Electrical problems can take huge amounts of time to find.

Please mark this thread Resolved so others will check it out if they have a similar problem.