Greetings!

1993 GMC 1500 4x4 Ext. Cab, 5.7 V8, 78,000 on it. It started a week or so ago, that whenever I am going uphill, the RPM's gauge jumps up and down approxiamatly 200 rpms. I cannot hear or feel a difference in the actual engine, but it show it none the less. Also, while going up hill, it stutters for half a second. The occurance seems to be random, and it almost feels like you are hitting a pot hole. There is no warning light on the gauges, and I will be hooking it up to and OBD reader soon to see if it comes up. FYI, I did a complete tune up about 5,ooo miles ago and also replaced the fuel filter and fuel pump. So any ideas?