I just bought my 04 srt4 88k miles a week ago and while trying to clean the cobwebs out i ran into a couple discrepancies. First problem I have is that I get like 80-100 miles to a tank around town then like 220 Highway, which seems odd. I have read several posts on here but didn't really get a clear answer as to why. What I was told when I bought it is that it has Seibens 1000cc injectors in it, a 93 performance tune and a punched cat. I know the injectors are for sure seibens, (idr how to spell it off hand) but unsure of the size of them don't know whether or not it has the 93 tune or not and the cat is for sure punched. He claimed 264whp and 304 tq which I also don't know whether hp and tq numbers matter in my case or if it's even true. And, every 30 miles or so the CEL comes on for 02 sensor. My question is, would this cause my terrible city mileage. And it doesn't matter if I'm putting around or hard in the boost around town it's still around the same mileage, 80-100 to the tank Now my second cause for concern is a shudder mainly when I'm in 4th gear under light acceleration no acceleration and deceleration. Once I slow down enough it goes away .Braking in and of itself doesn't change the shudder, but it does go away when I slow down below 30 or so. I have no issue at all with gears or the clutch, no grinding, no pops, all gears shift flawlessly, clutch feels amazing, but at around 30-45 mph or when I shift into 4th gear just cruisin' around I get it and I can only describe it as feeling like I'm on a rough road, fresh grated road or maybe like a flat tire, All my tire pressures are an equal 34 btw and the shudder is through the entire car, but it feels like it originates from the back. Now when I'm hard in the boost I don't notice a vibration/shudder at all through any of the gears. I got it up to 120 today and smooth all the way up and back down. Any help on these would be much appreciated. I don't want to go on a wild goose chase. I don't know where to start and this is the 1st srt4 I have ever owned or even ridden in for that matter. Thanks.