94CamaroZ28SS

Well i am posting this for a friend so here it goes....my friend has a 2001 Camaro SS M6 i think 77K miles........2 months ago he raced his car like usual and then he noticed smoke coming from the exhaust at idle.....so he figured he fried the rings.....he took it to the dealership and they ripped it apart and told him the #5 Cylinder piston needed to be replaced and that the other pistons were fine......he was upset cause all they did was replace that piston and ring and that was it..........well for about 3 weeks the car ran fine, but now it smokes even worse this time and we pulled his air intake tube off the throtle body cause when they put it back together they did a shitty job and the radiator hose rubbed up against one of the pulleys and you know what happened, so we immedietly noticed a lot of oil sitting in the bottom of the throttle body. he took it back again and the told him that #7 cylinders was bad, so he asked why dont they replace the whole motor and the told him there was no need. what do you thinkis cuasing the pistons to fail? please help.