I have lost alot of power in my 99.5 A4 1.8T. Stock, I was capable of merging onto a ramp reaching 80mph and now it takes me like 30 seconds to go from 40 to 65. Now I know a couple months ago a very little bit of oil was accidentally poured in my gas tank so ever since then I've taken notice of the decrease in power. So what should I check? Is it probably best that I take it to a specialist?

 

if your problem is related to the oil, it could have clogged your injectors, O2 sensors, fouled spark plugs, clogged the fuel filter, im unsure if it would affect a fuel pressure regulator but its something else to check. if any of those things are not functioning correctly it could result in loss of power.

if you havnt seafoamed that car since then, it would probably be worth your while to try that.

 

I have seafoamed it once and that helped actually. Thanks for your opinion. I didn't want to take it to a shop and replace/check so much stuff with nothing out of it except a high bill.