WVO has less BTUs then diesel so if your having trouble pushing 80 on diesel then i would not be suprised that you are down on power. The motor has some other problems like maybe low compresion or timing is off.
WVO will clean the carbon up very nicely all by itself, it is a great decreaser. I have heard of people running B100 with a cloged intake and within 2 tanks the intake will start to clean itself(as long as the egr is hooked up and working).

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82 Rabbit diesel (first d), 84 Jetta turbo d (300k when sold), 83 240d (305k when sold), 84 F250 6.9d w/Banks turbo(parts truck), 86 F250 6 cyl.gasser(waiting for 6.9d), 84 300d ( 347k Sold 8/04), Y2k New Bettle TDI (185k miles), 95 740IL (wifes), 87 300TD (206k Sold 7/05), 05 Passat TDI Wagon