I've got a A4 Sline Quattro tdi 170bhp standard, had a stage 1 remap and dpf removed and managed to get 220bhp more than enough. Looked into getting more but like some people said I would rather save my money. Intercooler, clutch , turbo, straight through exhaust and your looking £2500 min for good stuff. Once all that's fitted the next thing I would be buying is a new engine after it went bang. Focus on your torque bhp is more top end torque will get you there quicker. Or get a 3lt I seen one on you tube running 300+bhp probably only gets low 20s to the gallon.