bro, don't cross 90-100 km/h before ur initial 1000 kms. so, ur gear shifting should also be according tondis limit. and for installing A/C and that brakes issue give it atleast 5,000 kms running and then take it to any authorized suzuki workshop , they will service the brakes if u don't feel them gud at that time and then it would become much better. and when u install A/C of perform any other modifications ur car's warranty would become void.