Renault 1.4 RT problem

[AmDaMan]

Hi, just got my 1st clio, 12moths mot etc. Anyway small problems;
1) After i have been cruising for a long time then approach a roundabout to change geat it will stall then bump its self back to life, why?
2) Where the link pipe connects to the backbox it is loose, how is this tightened? please dont say i have to buy a new exhaust system[:(]
thanks,