VioletA

I just found this forum on the issue I am having but would still like suggestions and advice http://www.nissanpathfinders.net/forum/topic/11442-how-to-replace-evap-canister-and-valves/

I have a 2001 Nissan Pathfinder LE and I have not had any luck with this truck since I bought it 4 years ago.. Its now has roughly 173,000 miles on it...anyways We have a rear main seal leak that I am getting taken care of at the end of this month and I just had to replace the starter. And the muffler system had corroded at the flange of the tail pipe (rear muffler) so I had to replace that as well...I bought a Bosal Y Muffler system and just had it installed now my Suv is running funny not for sure if its a coincidence that it happened at the same time but this is what its doing: Feels like the idle is off, when I put it in Reverse or drive it vibrates and shakes but I feel it through the driver seat and the pedals, also some loss of power on the hwy its a struggle to get up any hill. My first thought was the muffler system and possible back pressure but I took it to the muffler guy and he said everything looked fine. Also I notice the new exhaust system I bought is not the same size as the OE and I asked if that could cause that vibration and he said no but he suggested that I do a tune up and have my spark plugs changed.. All I know is that it was not doing that before I had the new system put on..The size of the new muffler is quite smaller would that cause a problem later on down the road a? I'm contemplating ordering a different system to put on my SUV Also I have been having a check engine light come on but its nothing to do with the exhaust but it is in emissions its the Code P1491 Vacuum Cut Valve Bypass Valve I was wondering if fixing that issue is an easy job? Beings that its with the fuel system? And could that code and issue cause my truck to lose power or idle funny? We are going to attempt to fix it ourselves it seems pretty straight forward from what I read but I am inexperienced and will be going off of what I read and advice from others so any help will be greatly appreciated...Also I was wondering if you can change spark plugs as first timers or is it a job for an experienced mechanic?