New 2002 S80 T6 owner\new to volvo\site.. needs advice..

[S80T6_P_T_M]

Now I may be closer to stage 0. But still need advice... I changed oil\filter, changed plugs (.028), inspected plug boots. All old plugs were brownish in color, #2 as not. Checked all coil connections, wiring and grounds.. Car runs smoother an quieter in idle, but there is a slight, slight rough\vibration\shake... i also noticed after letting the car warm to temp the past few days before the oil change, I noticed an rotten egg smell, but went away after test drive. I have had a car battery emmit this smell in the past but its not the battery, but wait.. after the test drive or idling to temp, I hear light knocking/rattling in sync with the RPMs?? My first time under the car I spotted what looks long muffler along the area of the rear doors.. This is where I can hear rattling from best. vissualy I see the outters of this resinator\muffler pilling badly, I can hear it slightly from the tailpipe to. So the cold test drive was smother running, but acceleation is better but weak, never knew how an S80 should pull, this cant be all.. somethings missing. One thing i will do is replace all vacuum lines and out of curiosoty i want to perform a smoke test on the vacuum line system.
My questions are:
Did my cats take a dump i.e. rattling\smell\weak acceleration??
What vacuum line is best for smoke testing the system??
could the shake be mounts that are shaking the exuast as a part of the noise I hear??




please for give my typos as I broke my key board and its a struggle to type..
Thank fellas for any help...

[S80T6_P_T_M]

Okay today I checked all of the turbo hoses and found a slightly weak clamp or two and replaced. Still running smooth in park, but I let it warm up to get a feel for what’s going on with the exhaust. I know for sure the knocking\ rattle is coming from the resonator (before the rear muffler). I finished peeling the outer casing from it and gave it a few good blows with a hammer to see if it affects the noise. After a few blows to it the noise quieted, but I could still hear it. A few more hits and it stopped, 2 more hits it’s back again. Has anyone ever run into this? Would a good solution be to cut it off and install a straight pipe?? I also have concern as while in idle, the exhaust shakes a lot... Mounts somewhere maybe?? The cat seemed to be letting some steam\smoke\heat off in its area possibly burning off from a P/S leak that was everywhere but I fixed that 2 weeks ago. I am thinking the resonator or something is clogged somehow and I need help to figure the best diagnosis of what it could be...
Any Help is greatly appreciated...
Thanks

[S80T6_P_T_M]

So I fixed the resenator rattle issue and there is not a clog in the Cat.(no CEL) I have the car running smooth in idle a little rough when the rpms get higher, and while driving. It still seems to be in limp mode and is very sluggish while accelerating and the car does not want to go. So with that said, I want to look for my next task at hand.

I want to perform a vacuum leak test on the whole system, what would be the best method smoke or presure test? I will also look to get a new tank of gas and a new filter as the gas in the tank is almost empty and is at least a year old. One question I have is what is the best way to rest the computer to have the computer re-adapt to the engine?? I read that I can disconnect the negative terminal and touch it to the positive for 30 seconds and that will clear it. Not sure if that works but by me just disconnecting the battery for 20 minutes did nothing. Is there anything else I should be looking at or testing.. getting close to a brick wall here.. I an greatful for any help..



Thanks

[S80T6_P_T_M]

Thanks to all here that responded, I nailed the misfire issue. J J..I had a bad #3 and #4 coil pack. I replaced them and the new toy has balls and potential.. Made me smile from ear to ear that its good now. Although I am having another issue and I am thinking and hoping its small. At the beginning of the test drive as I pulled away slow but steady there was a stumble during acceleration, but right after it took off.. I on the way back I cruised at about 40mph and sopped, I know there’s an ETM but when I went to take off again it pulled very little but it was as if there was no cable\signal to the ETM at all, pedal goes to the floor and no go. All while this is occurring the car is at Idle with little to no change in idle as I pressed the pedal. I was lucky I was still rolling about 25 yards from the garage. I looked to see what was up and I noticed while I was putting it all back together I had an issue with the intercooler hose clamp which was resolved but this made me forget to tighten the turbo intake hoses. So after Tightening them up I cranked the car and had like a weird idle, but after a few restarts it was good again. Did not have time to test drive again or scan for codes so Ill shoot to do this tomorrow..

Does anyone know what might have happened here?? I believe it was the intake hose possibly making the MAF act up but would love some input or other opinions.

I have completed the following to the car and would like to hear what should be my next replacement\maintenance or Mod. Keep in mind I will get to the trans and will at least flush and fill, but what else should I go for?? Thanks to All Again

Changed:
Plugs + #3,#4 coil packs
Oil & filter
Clamps, and a few hoses
Air filter&fuel filter
Silencer (want to go with Cat back system but not sure on a muffler or pipe size to go with)
So far not bad for $1000 for the car and $200 in parts…. In my book anyway.