So I just bought this LS400, I did a relatively thorough job looking over it before buying it, everything seemed to check out besides a few minor things like the antenna not working, seems like no power or even attempt to create a display on the climate/clock LCD and the power mirrors not responding(problems been fixed, picked up a new ECM from a junkyard for $15) the car drove great around town and on the freeway I felt like I put it through its paces pretty well and no issues arose.
I took the car home and started looking into it a bit more thoroughly, I pulled the plugs in one bank to look at them and they all seemed to be in good shape so I assumed the other bank was good as well, the wires were still very flexible so I assumed those were good and out that back together, I checked the air filter which ended up being almost black with some saw dust all over it as well so I replaced that, while I was at it I pulled the rest of the plastic intake piping off and checked inside the the throttle body which was caked with carbon as was the back side of the butterfly valve, I sprayed down the inside of the throttle body with throttle body cleaner and tried using a tooth brush to pull off as much as I could, I put everything back together and rent for a drive, the car ran great. I took it up to costco threw a can of seafoam in the tank and filled it up, directions say 1oz per gallon so I figured I was safe. I got on the freeway just fine. I ran it pretty hard figuring I'll start pushing it through it got up to speed no problem but then as soon as I settled in around 65 I realized that if I would try to just lightly accelerate the car would sort of stumble or stuggle. I punched the throttle and it picked up went no problem, it seems to only be light to mid throttle application above about 45mph that causes this to happen, since then it also seems to kind of surge or want to lurch when I'm stopped with it in gear, D or R if it throw it in neutral there's no problem at all.
Does any one have any idea what may be causing it to do this? It ran fine after everything I did until the seafoam, which seems to be the go to solution (no pun intended) for issues like this, I drove it 150 miles and topped the tank back off hoping diluting it might help and have driven another 100 with no change at idle or freeway speed.
I had searching for a topic that copies before posting and none of them seemed specific to this, sorry if I missed, the common issue I saw also included low idle and stalking which I don't have an issue with.
Any help would be greatly appreciated, thank in advance
