I have a MK4 Vauxhall Astra 1.6 16V.
I was thinking about tuning it a wee bit. Easiest option people will suggest is add another engine but my current engine is in fantastic condition. So I am looking to keep the current engine and tune it as much as possible. I thought about taking it to Dastek to get the car chipped as this will add around 15bhp for under £300. My car is booked in for a full custom stainless steel exhaust system next month, I may get an air filter to so that should add around 5bhp max. I was thinking about de-restricting the airbox. I looked at a manifold a while back which supposedly added 22bhp but that was £800. How do I go about polishing and skimming the head? What does this do etc? Any other modifications you can think of. Looking to make the car faster than the usual standard 99bhp.