Ok so you had the basics checked , now i take it he did not do a fuel distributor test, as for injectors you have to clean them in the injector tester before installation in the vehicle due to they are coated from the factory. I would stress on doing the cylinder leakage test and the fuel distributor test. This is only if you really want this car perfect. It is not uncommon for a fuel distributor to be partially clogged. The easy way to test this is if you have the car on the scope and do the cylinder balance test and one comes up low, lets say #3 is low well take the line from #4 and put on #3 and vise versa. If the cylinder changes to #4 well you know your problem and you had better check for contamination in fuel system. I have one in the shop right now I am replacing everything from tank to injectors . Diagnosis on these cars is fairly easy its just knowing where to go. Weirdest one I have had yet is a rough idle and it ended up being fault of rubber in brand new air rail wasnt punched out all the way. Good luck
