hey, my truck used to do that between 60 and 70 mph. I had on the stock tires and they were kind of worn down. I got Toyo proxes S/T tires and now it runs smooth silk at any mph. I hope this helps you!
White '94 #4000 of 4007
1.7 roller r's
mallory hyfire ignition
ASP underdrives
K&N
Bassani shorties
15.2 @ 88mph on the toyos.
