First of all, there's no such calibration in grande. It's literally an animal beat it for 100k km and even then just clean the strainer and add fluid and beat it more it's gonna say okay master.
When you press paddle it means you are increasing tps value, and increased tps value means more fuel. So if your injectors are clogged and you're pressing throttle again and again and it starts abit better. I would say it seems like it is faulty injectors.
But my advice would be, for a peace of mind money doesn't matters too much. So let that guy add injectors see what happens next day. If the starting improves which looks likely will... Go to him or any renowned guy again, buy new fuel filter plus strainer and get it installed...
Always delete ambiguity. If you add Injectors it's gonna stay in your car, if you are gonna change filter, it's gonna stay in your car. It's a fueling problem so even doing both will doesn't make this fact change that it's your car. When its your car, to get rid of this problem and ease your life you should not think too much spending on it.
Just do step wise, tell that guy you will take back your injectors as it is. He will give you new injectors and rail, on this agreement that if for two days your issue doesn't disappear he will return the money back.
If injectors solve the trouble give him 500 rupees tip, praise him & tell him to replace fuel filter aswell. That's how things work. I hope you understand my point.