I just purchased this 1987 300TDT and it is my first diesel car (I do own a diesel tractor). It has 96,000 miles on it. At start up it runs rough, as if it is only running on 4 cylinders and it smokes alot. After about 1 minute it runs perfect.It runs better if I cycle the glow plugs twice before starting it. I thought I may have a couple of bad glow plugs but in the complete set of reciepts I got with the car, I noticed all the glow plugs were replaced two years ago....Any ideas?