My 2001 k11 had orange engine light on. got it diognosed as topfront lambda sensor. I replaced this with an original bosch part/not aftermarket cheapo. Garage re-set the engine management system light, and way hay it stayed off for a while, but came back on after aprrox 50 miles driving. garage re-set engine light again and same thing happens, light comes back on. the car will accellorate well but if you release accellorater pedel for a moment then hit the gas again its seems very flat and unresponsive for a few seconds before continuing to accellorate? Any ideas greatly appreiciative. Have checked MAF sensor all looks good and no other faults shown on engine managment!!! TIA in advance