Hey,
I'm not familiar with your T4, but I had a similar setup on my '96 XR4 with UNI, no snorkel and XR's Only pipe. I'm in NW Florida, basically right at sea level. Xr's Only set me up with the 160/60 combo when I bought the pipe. It was a hair on the leaner side, but fattening up the fuel screw helped. The bike ran really well, very crisp throttle response etc, clean revs. At 162/62 you should be plenty fat, make sure to adjust your fuel screw, and fatten up your needle setting before you go for a 65 pilot. Keep in mind, I've never had an aftermarket pipe that didn't backfire a little. Backfiring can be a sign that you are lean, but it can also backfire when you are too rich. However, the lack of backpressure on aftermarket pipes has a big effect too. Play around with what you have now, fuel screw, needle position, check your plug, before you go getting to fat, that's not good for your bike either. Good luck, and don't jet your bike by whether it backfires or not.