i have a problem with my astra when i got it there was no cat in exhaust system drove it to work and it stopped three times on return journey the same happened again since then i have fitted a cat a the car was running in the garage for 30 minutes plus and it did not stop can anyone give me any advice on what the problem could be?Also there is a very heavy smell of petrol when running and the hydraulic tappets are making a clicking noise any advice on this please i would much apprecite it