tahoe "bump" while driving

I have a 1998 4 x 4 Chevy Tahoe with 75,000 miles. At 72, 000 miles I had the intake manifold replaced and since this time and many trips to the dealer there is no solution in sight. The dealer has driven the car hooked up to a computer with no codes registering. The tech drove it home for 2 days.

When driving down the freeway the car "bumps' or lugs for a split second and then is fine. There is no movement on the tach and it only happens intertmittently.

Three of the fuel injectrs have been replaced, new plugs, new rotor, new wires, cap.

Anyone with a solution would be much appreciated.

thanx

I had this issue on a '95 and since they made a lot of changes in '96 or '97 (whenever the "vortec" came in), I don't know if I can really relate--but anyhow, had the fuel pump replaced and that fixed it.

Appreciate it.