Altaf Khalifa helped me source a pre-production version of an exhaust by Quickshift Racing for my Hero Impulse.
There is a significant improvement in the mid-range torque although the top end stays largely the same. Now it takes a lot lesser time for me to reach 80 kmph. But the increase to 100 kmph still takes its own sweet time, which is expected given the engine capacity. I was missing some grunt at low and mid range engine speeds and it seems like this exhaust has filled the gap nicely.
The exhaust sound is nice and gruff with the db killer left in place. Thankfully, the motorcycle has stopped sounding like a washing machine.