I bought a Mazda 3 2005 1.6 diesel with a split inlet pipe have replaced this and car will still not rev above 3000 revs drained 2 litres of oil out as it was up the stick and oil in the air filter no smoke when running any ideas where to go next engine light on on dash

 

I would buy a OBD code scanning tool and plug it into the diagnostic plug; you car may well be able to tell you what is wrong with it.