Hi Roshan, The standard 1.8 can take a lot of tuning as it's not much different to the 1.8 Turbo. The best thing would be obviously convert to a turbo. If the mileage is getting up its worth de gunking the engine with some "magic spray". Suspension will improve the handling but make sure its a good quality kit. The GENERIC ones that FIT ALL TYPES OF A4's are a rubbish compromise - don't go lower than a 3 cm drop if you still want to drive it round town. If you get 19's make sure you have ultra low profile tyres but i'm sure you will be dissapointed with the ride quality. Fitting good quality tyres with a directional tread would make a big difference. I found on my 1.8T that an induction kit ruined low down torque so just go for a panel air filter.