Straight pipes are inefficient even on a carburated engine, put them on a computerized fuel injected engine and you've basically gutted your motor. Your power band will be narrowed and loss of power at all but optimum rpm will be lost. Your only fix would be to install "tuned" pipes. Dragsters use straight pipes cut to a specific length for a specific rpm only. In the real everyday world they aren't worth a hoot driving around a varying rpm's.
Regarding the tire, Victory uses radials do they not? Harley as far as I know doesn't. Your chassis was engineered for radial tires and by using a radial on the rear (I assume that yours is) and a bias belt tire on the front you're setting yourself up for some handling issues. I highly doubt that balance beads would solve your problem but you can get ones that are small enough to put in through the valve stem and try it.
I'm gonna rant a little here so bear with me. I really don't understand why some folks think that they are smarter than the engineers who design vehicles. There are some things that shouldn't be messed with. Yes you can change the pipes and tuning to achieve higher torque and horsepower that the factory because of EPA rules can't do but changing to straight pipes simply because you like the racket will net you one thing, more racket, not more power. In the days of carburetors we could tweak intake, exhaust and cams (if we were good enough) to make a boatload more power. Unfortunately in todays world it can still be done but normally not by the owner of the bike. You have to pay big bucks to have someone else design the mods even if you yourself can install them for just a few more ponies. Personally I'd rather spend my money on fuel so I can go kill bugs with a few less horsepower. The same goes for switching to bias versus radial tires. The chassis is designed for one type of tire "radials". Using bias tires defeats all the testing and engineering that went into making a Victory handle like a Victory and not a Harley.
Sorry for the perceived beating, it's nothing personal and I'm sure others will chime in and crucify me for my thoughts.
Gotta agree with everything said. I probably wouldn't have gone into the rant because I tend to modify the hell out of everything I own (almost always with good results but I spend a shitton on my mods) but otherwise I'd bet the advice given is spot on.
Chasing problems that pop up after a mod is frequently a losing proposition. Undo the mod and see if the problem goes away. If it does, your mod caused the problem so you either need to live without it OR spend the money necessary to redo it correctly.
You said you have the victory genuine pipes with a loydz airbox and pc5 but you didn't say who built your fuel map for the pc5. A PC is only as good as the map inside it. If you're using a map downloaded from their library that should get you close (assuming the map you downloaded is any good, not always a good assumption) but not perfect. And each map is only good for the mods listed. So for instance if there wasn't a map for the vic straight pipes with loydz airbox and you grabbed one for say vic straight pipes with k&n filter, your fueling will be off. Take the bike to a dyno, pay to have a proper map built and your problem should go away.
As for running out at 160, we already know your motor isn't running correctly so until that's fixed there not much reason to chase this issue. However, 160kph (or roughly 100mph for us 'muricans) is a bit slower than I would expect for a top speed but not necessarily for a 1/4 drag. Don't forget you're on a big heavy bike with HORRIBLE aerodynamics. Weight hurts acceleration, having the drag of a billboard hurts top speed. You're never going to touch the speeds of a sportbike unless you throw some serious money at the thing.
Tires were explained by Joe. Make sure you have the correct type of tire on the bike before you start chasing balance or other issues. Bias tires behave very differently than radial and the two are NOT interchangeable. Different brand/model tires front rear can sometime cause handling problems but not always. For the sake of diagnosis though I would make sure I had a matching set so if the problem is still there I could eliminate tires as a possible cause.