Rough and high idle

[Bird77]

Hey there, new to the site. Got an issue with my V70. It is a 2001 V70 non-turbo with 264k miles. I got the wagon from a co-worker as she was going to junk/donate it due to it one day just losing power and her having to drive on backroads and side streets to make it home. I got the vehicle from her after it had sat for some time so after I got it home and finally started I took it out for a drive. No power whatsoever and would not go a mile over 25, tach surging up and down. Research pointed to etm cleaning needed or possible failure. I took the throttle body off the intake and first thing I noticed is the plate is not fully closed and heavy carbon build up. Ah ha! I go to push the plate open and it is hard to push open and does not shut on its own - failure. Head to a local yard and find a wagon with the tb with the yellow tag. Installed the “new” tb and idle stabilized but then sounded like a misfire. Sprayed some carb cleaner around the manifold and when it hit the drivers side it would sound immaculate for a couple seconds before going back to crap. Ok, vacuum leak on manifold. So since I was going to replace the intake manifold gasket I decided to see what else could go wrong. Read about the pcv trap clogging and possible clogging of return in block, decided to give it a look due to the advanced mileage. For the record, I didn’t find dropping the oil pan to be too difficult. Blocked. Solid into the block. Spray with cleaner, chip with screwdriver until it broke through. Chunks of buildup fell out onto my driveway. Check the pan - same thing. Cleaned the pan, changed the gaskets and put the pan back on, filled it with oil, started it up - no leaks. Had a vacuum issue due to me not remembering where I tucked one of the hoses but once I found it everything was ok. So now the V70 starts, runs no problem. The idle is high - 1100 rpm - and a little rough. The exhaust also pops, like a muffled backfire. Here is a link to a video I recorded:



Whew! So for a quick recap
2001 V70 base
264k miles
New gaskets in oil pan/manifold/tb/injectors
New pcv
“New” tb
High/rough idle

Have an obdII scanner but it’s a generic one and it takes forever to pull anything. The codes that it pulled are:
P1026
P1620
P0507
P0300

These were pulled prior to the “new” tb and I know that one coil has been changed previously. I guess what I’m looking for is a little more insight. I know the P1XXX codes are not Volvo specific, I plan to get it to an indy to scan it but what am I possibly looking at? Do I have to worry about the iac? O2 sensors? Clogged cat?