2001 VW Beetle 02 sensor car will not go over 65mph

I have a 2001 VW Beetle 2.0 engine with 171,000 miles on it. I have a check engine light on saying that bank 1 lean. It has been like this for years and I have had no problem with it. Yesterday I discovered that my car in 5th gear will not acclerate any faster than 65 Mph on the highway. My car is a 5 speed manual. When I am in gear 1 for example I can only go 15mph no faster. The tacmeter is a 3,000 and the same in 2-5th gear the tac will not go over 3 grand. I changed the air filter thinking it could not breath. I can smell that my car is getting gas so I know it is not the fuel pump. Then after work today is started working properly again and then I shut the car off and turn it back on the car turns over many times before it will start. Then I drive the car again and it is doing the same thing where it will not go any higher than 3 grand on takometer. Need some help. It also seems that the tail pipe is black the car I think is running to rich… Please help!