And i'm pretty sure if it were an injector prob and whas gushing fuel the lamda sensor would had caught something and most likely would had shown some kind of fault-error..
Meaning for a whole set of 4..although i'm sure it won't feel the same if you compare them to the yellow koni's..these are more street use-sport feeling than the more firm and track oriented yellow ones..your choice..
It has done 30000 miles on the same pads what did you expect?99% brake pads..maybe even have a look if the car has more than 60000 miles most likely the discs will also need to be replaced..
If you don't include the cat anything you do will give 0 power gains..all the power from exhaust mods comes from headers and somewhat from the cat..The only point fiddling with the rest of the exhaust is clearly to have a better exhaust note...widder pipes are a must if you have something big...
You could raise compression by skimming the head,porting is also a must if your getting the head out and go for 1.3 cams.They are a straight fit to a 1l and is worth doing..this could make at least 10hp from stock...mine made 86.5hp with a 9.2nm...but i also have a full custom exhaust and header...
Look everything is possible..it's how much you want to be involved and made get your hands dirty...i believe you could go for an other kind of profile where you could ensure not much fuss to time the engine and no compression loss...(usually big duration tends to lower a bit of static...
Really high profile cams will mess up with you timing(meaning too much duration and lift you will need adsustable cam pulleys)so proven that 260 duration and 10lift is something you can go for without having to mess with timing marks,retarting ect.. although 260d 10l means that the car will...