A couple of weeks ago, I played Infernape 4/ Luxray G deck at BR. The deck performed really well. I made top-cut after going 5-0 in Swiss. It's a strong deck, but in my experience, it has some problems against MaChamp, Gengar, and Mewtwo. I've tried a lot of different techs, but these match ups are still tough. You have to disrupt set up really early to have a shot.
Machamp - Take Out, Hurricane Punch, and Machamp Lv. X all cause headaches for this deck. I play 3 Unown Gs, but having to attach those rather than Energy Gains is a real hinderance. Luxray G is an OHKO from Hurricane Punch, and Infernape 4's attacks can't keep up with Machamp when you can’t use Energy Gain. I tried Uxie spam, but still I have yet to win a match up against Machamp, where starts were equal.
Gengar - I haven't found a way to get around Faint Spell reliably. Nidoqueen makes it almost impossible, and she keeps your spread damage to a minimum. Also, you have lots of Poke-Powers on your Pokemon. It’s hard to get Unown G on them all. Of course, you can chose not to Level-Up, but that's advantageous for your opponent.
Mewtwo - Intimidating Roar and Bright Look aren't enough to get around Mewtwo. You'll be able to circumvent him for awhile, but eventually, you'll be stuck with just Mewtwo. Without away to KO it, you lose.
I've tried lots of different techs, but the problem is too many techs make the deck inconsistent. Here are some techs that I’ve tried.
Toxicroak G and Skuntank G - Require 3 to 4 deck spaces plus Stadiums, which you need a reliable way to draw into.
Dialga G Lv. X - Requires a minimum of 2 spaces, and when you Level-up, you'll need away to retreat safely to the bench to fully utilize Time Crystal. You could waste 2 Energies, but that's not really possible a lot of the times. You'll need Warp Points or Switches, and, like Stadiums, a way to reliably get them.
Houndoom 4 - Requires only 1 space. I like this tech. It's helpful against Gengar and Dusknior.
Ninetails (MT) - I thought this was the magic tech. I put a 2-2 in my deck, thinking it'd help against Flygon, Machamp (via using Color Swift on my opponent’s Uxie), and Mewtwo. It got mixed results. It was helpful, but it was also hurtful at times. Vulpix starts aren’t good and Ninetale's Fire Blast discards a :fire: Energy, so to retreat it, cost another Energy. It couldn’t hit-and-run like I’d hoped. Also, I had trouble getting it out quickly when I needed it.
I'm not saying these decks are bad. Actually, I think the quite good. I had some issues with it and wanted to share my experience.