Tracks gives us parts according their level mostly:
1-5 lvl:
T1 street parts (improved, sport)
6-10 lvl:
T1 street parts (improved, sport, tuned)
T1 race parts (improved, sport)
T2 street parts (improved, sport),
T2 race parts (improved)
11-15 lvl:
T1 street parts (tuned)
T1 race parts (improved, sport, tuned)
T1 pro parts (improved, sport)
T2 street parts (improved, sport)
T2 race parts (improved, sport)
16-20 lvl:
T1 race parts (tuned)
T1 pro parts (improved, sport, tuned)
T2 street parts (sport, tuned)
T2 race parts (improved, sport, tuned)
T2 pro parts (improved)
21-25 lvl:
T1 race parts (tuned)
T1 pro parts (tuned)
T2 street parts (tuned)
T2 race parts (improved, sport, tuned)
T2 pro parts (improved, sport)
26-30 lvl:
T1 no any part (26 may give tuned)
T2 street parts (tuned)
T2 race parts (sport, tuned)
T2 pro parts (improved, sport, tuned)
31-35 lvl:
T1 no any part
T2 pro parts (tuned)
T3 street parts (improved, sport)
T3 race parts (improved)
36-40 lvl:
T1 no any part
T2 no any part (36 may give tuned)
T3 street parts (improved, sport, tuned)
T3 race parts (improved, sport)
T3 pro parts (improved)
41-45 lvl:
T1 no any part
T2 no any part
T3 street parts (tuned)
T3 race parts (improved, sport, tuned)
T3 pro parts (improved, sport)
46-50 lvl:
T1 no any part
T2 no any part
T3 race parts (tuned)
T3 pro parts (improved, sport, tuned)
Thats all