Hello everyone I just joined..and really need your help on my s40 04-05 volvo.. my check engine light is on. I've changed everything from the fuel injector to the O2 sensor... also my drivers side back seat floor is always wet when it rains... I've been to several so called import shops and same results... Help

 

Get your fault codes read to accurately diagnose whats amiss and advise back to forum.
Guessing and replacing parts perhaps needlessly is costly.

Do you have a sunroof? The wet floor could be due to blocked up sunroof drain tubes or a leaking heater core although you would smell coolant odour with the latter.
Also check the front/rear door rubber seals (at top) are in okay condition.