Speed EC3

Hello together, I have a problem with my EG3… which does not drive faster than 160….Bergab sometimes 170… Wonders me a little since the box of my Ma still drives loose 180 and has good 100tkm more on the clock. From a work colleague of the EG3 comes even on 200 lt. Tacho. Think such big differences can not actually exist or ? Now the question is what is going on with my box. Filters and candles are fine at least I cleaned the filter in March and ne If the cylinder head gasket was leaking I think I would have an oil film in the cooling water and see it on the candles or ? What else can this be ? I bought the car last year in June, previous owner was an older gentleman … So at this time the 39tkm had actually nothing on it …. After a change of oil in spring the box has already kicked correctly several times but Can the carburettor be adjusted or is it due to the ignition ? I have no idea and would hear your opinions … Thanks already greeting h0nk