I'm currently going through my S60 T5 with new plugs, injectors, pcv, I'd soon like to get a few more ponys out of it once I'm done the basics. I'm unsure if a tune is the way to go for a first step or if someone knows of something more worth my time and money. The car is getting up there in km's since it is a 2001.

 

ECU tune is the best way to get more HP. A lot really depends on what your total HP goals are and your budget. An ECU tune can add 30-50 HP but to go further you will wind up with a series of different bottlenecks. If you decide to replace the injectors you can upgrade to ones with higher flow rates. Next is to get more air through the turbo you consider a bigger downpipe (ie 3"). Now you have to make sure your engine is in a good tune (plugs/coils, synthetic oil, filters). I wouldn't worry about the intake air system - factory is pretty good, but if you are now over 300 HP you'd want to change the transmission fluid and start managing the extra heat - larger oil cooler, intercooler, tranmission cooler, check out using water wetter additives in the coolant. You can also move up to a bigger turbo - check out ARD Tuning for upgrades. I believe your car has a 16T (16 refers to the air capacity) - there are 18/19/20 sizes that will work (you can swap the impeller and keep your housing). There are turbo bits like blow off valves to help spool up and driveability but now your about $5000 into the car with enough HP to fry the transmission unless you have a manual... Personally I'd do the ECU tune, injectors, downpipe and hope for about 300 real HP for 5-6 sec. 0=60 and 13-14 sec 1/4 miles.