Commentary:
(Not taking into consideration Infernape Lv. 40.)
Alone, Infernape Lv. X is a decent card. Flare Up can be troublesome, but the 150 is worth it. You've just got to make sure you can get those cards in the discard pile. There are plenty of ways (without getting KO'd repeatedly), but I'll go into that below. However, Burning Head can help. If you get the cards back in your deck, then it's no problem discarding them.
Combos:
Infernape - DP I felt this should go here. It can get you 90 damage with Flare Blitz, and discard energies. Yes, it delays the set-up, but some cards (Ex. Energy Switch) can help.
Delcatty - PK I was confused about this at first. Everybody was saying it was the "only" card Infernape worked with, so I decided to look at it. Energy Draw is good, but it can take a while. Plus, if I only had 1 energy in my hand, I'd personally rather put it on Infernape, instead of discard it.
Magmortar Lv. X - MT Aha! Something other than Delcatty! Yes, Magmortar can go well with Infernape, too. Flame Bluster discards 2 energies per attack. Also, regular Magmortar is useful, too. If you decide not to use Magby, you can discard 2 energies, too. That's 2 each from both. Not that bad.
Gyarados* D - HP This is a risky card, to say the least. Not only is it a * Pokemon, meaning you can only have one, but its attack, All-out Blast, nearly decks you. However, I would say it's worth it, if you're one to take risks. It does 50 + 20 for each energy discarded. Also, with Infernape, you can switch the next turn, and use Flare Up repeatedly, depending on how much energy you've put into your deck.
Score:
Modified: 9/10
This card has more combos than one. The only thing you can do is mix and match, and try each one. It's a remarkable card, and I can see why it's popular.