Hi , I had some noob question to ask , I had a injection 4g91 in my iswara , I wish to know what upgrade can be done to let it to be more powerful and fast .

I want the best upgrade to be done which does not always cause problem had to repair .

Can all sifu sifu teach how to mod ? mod by step by step like change which part then next stage change which part again ? And if change which part had to change together only will do .

Please list down the modification with the COST also...