Engine Performance problem
1998 Peugeot 306 4 cyl Two Wheel Drive Manual 51000 miles

hi ive got a 306 2.0 xsi with 51000 miles and the cam belt tensioner went so i had a hefty bill but had to replace the head, valves the tensioner and water pump with the local mechanic, but ive got it back and ive done bout 150 miles but sometimes it feels sluggish wen u put ur foot down but this is only sometimes about once in 15 but other times u put ur foot down and the car flies please please help