Finding it hard to Shift at higher RPM's

Ok, here's the scoop. I went to get the Tranny Oil changed, now I noticed for some reason my shifting got harder afterward. I though "Ok, maybe the oil needs to sit in or something"

So I drove around like that for two weeks, and it didn't get better. So I go back and I ask these guys what they put in, and they told me they put in Castrol Syn ATF. So I say "Crap, the Service Manual says to put Mercon or Equivalent in it" So they change the oil again, and I drive around for like 10 mins and I notice shifting got even worse!

Crap, so I go back, and I go "Are you guys sure you put Mercon? Shifting is even worse now!! Turns out they put Mercon V. So I know "No man, it has to be Mercon, not Mercon V, they're not compatible!"

So we look on the net and find that Dexron III is Mercon compatible. So we put that stuff in. Immediately I could feel the difference in shifting, it got a lot smoother. I've been riding it like that for about 3 days now, and I notice that the shifting never got as smooth as it used to be before this whole thing even started. It still shifts slightly harder than I remember, and it's especially harder when the RPM is high :( (Also 3rd gear seems to be harder than the other ones, and I've heard there's a known issue with 3rd gear on the T5's)

What the hell? To top it off, about a week ago I forgot to take the thing out of reverse and I let go of the clutch pedal. The car jumped back like a horse got kicked in the balls! (Engine was running at about 1k RPM) and to add insult to injury, I still had the parking brake on, so the car jumped and struggled for a couple of meters before the engine stalled. Now I have this slight gas odour coming out of the engine. I wonder if I busted a hose, or an injector seal.

Sorry for ranting guys, but I could almost cry, I'm gonna destroy my own car out of sheer stupidity :( Mechanic's gonna look at me like "You were just here 2 weeks ago for a clutch replacement? you're back already?" :banghead: :uhoh: :(

So anyway, I took a look at the gas smell, and it looks like it may be a gasket in the headers that's screwed up. Possibly a hole in the tubing, don't know for sure, gonna hoist the car up over the weekend and try to trace the smell.

Also since the Oil Change I notice shifting is either easy or hard, intermittently. If it was the syncros, I imagine it would happen all the time. I was planning to go to the dealer and have them put in original Mercon ATF, you guys have any better suggestions?

Also once in a while I find going into Reverse is impossible, even if I try to shift to another gear first. It's like when the syncros are lined up it just goes in, but if they're not, then it's ridiculously hard. I was told that mechanics don't recommend changing the oil, because it can make problems worse, since the sludge and stuff is flushed out. I don't know if that's truth or not.

Thanks for any advice in advance guys!.

You should shift into a gear anyway before going into reverse so that your synchros line up, even if your not having troubles.