Dear xBhp'ians

I own a Suzuki GS150R bike, Aug-2010 model, done 39600 km on ODO. Always regularly serviced. I used to live in Pune, recently shifted to Mumbai.
I am having following difficulties on my bike

1) For past 1 year, my bike draws constant 40-43 kmpl of mileage, it used to be 50+ earlier
2) There is a lot of engine noise
3) Original smoothness/thrust from bike is missing, low pickup
4) Vibrations

I've tried almost all the Suzuki Service Centres in Pune, no luck, they always do the CO setting and it doesn't help. I always ride my bike in 55-60 kmph range.

I also did a Motul 15w50 engine oil recently and not the OEM from Suzuki, its giving me a bit of refined performance, but it still doesn't run as it used to be 1.5 years back.

I really love my bike, its a beast out there in 150cc segment, I want your expert advice and suggestion on a decent service point for Suzuki GS150R in Mumbai as I am new to this city.

Cheers and Thanks in advance
Naveen