94+ Brake upgrade pedal feel

Hey guys,
 
About 8 months ago, I posted about having some issues with my brake upgrade. Calipers locking on and overheating and whatnot.
Since then, I've discovered that it was due to a) my ABS playing up, which will be removed fairly soon, and b) my right-rear caliper being seized and needing a rebuild.
 
Since then, I went to Wakefield park and tracked the car for the first time. While I was there, I noticed that once you get up to speed (~120k's or so), when you try braking, the pedal is totally solid for about half a second, before it gives way and the brakes start to work. Anyone who has Gen 3 brakes will know that there's a bit of a dead zone before the brakes bite. This only happens when braking from high speeds. While daily driving, I have no problems, but since running semi-slick tyres on weekends, I've been noticing this while in the hills as well.
 
There was a thread I was linked to a couple of months ago indicating that it's a check valve issue, but that didn't really help, since I don't know what the difference is between Gen 2 and 3 chassis regarding the brake booster operation.
 
I have a Gen 3 Bathurst wreck in the back yard, which will still have all the parts I'd need to fix this issue, I just need to know what needs to be changed, and the repair manuals are telling me nothing.
 
tl;dr, apparently I have a check valve issue. How do I find out what the difference is between the old brake booster and the new one?
 
Thanks guys!

Right, so if I check through the Gen 3 chassis along the line the booster runs off, I should find the check valve that runs off the manifold pressure? The engine has since gone in my car, but that line is still running the length of the car.
 
Thanks for the help!

I have both boosters. I've got the '91 one sitting in a cabinet, and the '94 one on the car at the moment, along with the rest of the brake setup.
 
I just went out and inspected both engine bays. I noticed one difference between the two lines. The photo is of the Gen 3. That rubber line isn't on the Gen 2 line at all. It's solid all the way around.
 
Is this what I'd need to put on my car?

Awesome! Good to know that's an easily fixed problem now.
 
Thanks guys!

It's not an issue until you start slamming them on from high speeds. They work just fine until you're heading into a hairpin from a long straight, or similar.
Less then fun, though. I'll admit. Glad to have this issue fixed.
Or at least close to.