I would increase the price of the upped by 1... Just to equal out. I would also decrease the Spell Damage of the unnuped by 2... That's why too much firepower for an unnupped with a cost of 4.
Hmmm, I can't help but think it would be UP with those stat drops. The 6 damage is only 2 more damage than a standard attack would do (assuming no shields) so it wouldn't seem worth detonating for an extra 2 damage (or more depending on shields). I mean, there are circumstances when yes, detonating for 6 would be worth it. But how many times compare to the current 8 damage. I, personally, would rather drop the normal damage than the ability damage.
As for the costing (which I feel I should explain), it was worked off the upped Unstable Gas, costing 5
and using
to trigger. You can only have 6 of both of these in a deck so we're the same there. UG needs a duo so the cost for this in a mono goes up. However this does half the damage and doesn't affect creatures so its worse in that way. Its probably harder to remove a Creeper (safely) than an UG so it's better there. The ability can be trigger on the turn it is played but at the cost of a wasted card so its about even. The 4 attack isn't much (I'd say) in the upped meta. Destroyers and MPs are both much better for damage to cost ratio. When I think about all that, 4
just comes to mind. Then the unupped is just a weaker version with the same cost.