well you have a used car, you just bought. sounds like it needs at least a few things. some where i have a list for projects like this...oh yea in my head, it may take quite a bit to freshen up just about everything. thats just me, as these cars run good when treated right.
like said, sounds like you just bought this car. so go buy a new fuel filter, and air filter. you also need a can of diesel purge, you ll have to find a store around you that has it in stock, sometimes napa, advanced or autozone may carry it. you need a few items in order to 'bottle feed' cleaner/flush. length of fuel line (i prefer f.i. line), and a connector, you should be able to find in a plumbing shop. fuel line should be 3/8", the connector 3/8" to 3/8".
running a full can straight can have the best results for cleaning injection system. find a place to put the can, can be on the side of the air box, hopefully its kind of secure, take the inlet line off of the fuel filter, insert connector, take a good length of fuel line, put on other side of connector, this one runs all the way to the bottom of the can. take another length of fuel line(you ll cut the line you buy, maybe 2 feet or 3), this line you put on the pump return, and run this also into the can. put the can in a good spot, maybe use some rubber bands to hold it.
i think your ready, you go in, of have your help in the car, and start it. run at different speeds, and at idle, up to about 2000rpms, maybe some more, run the can out. again change engine speeds.
afterwards take lines and connector you put on for flush off, put in a good spot to use in the future, put new fuel filter in, prime, you can do by the return opening, with additive or fuel, or by the inlet, put fuel line on and a funnel and add fuel or additive. dont spill! secure filter, add additive to the inlet line, to prime, dont fill all the way up, connect to filter. notice i didnt say add fuel to inlet line. here it needs to be filtered. put in new air filter. check air box, it may be dirty.