My 2000 SSEI runs great with only one problem I can't figure out. While on cruise at 65 mph 1700 RPM or so and going up a hill the boost guage goes from -10 up to 0 then when it gets to 2+ it starts this bucking. Like ******* it. If I put my foot in it it runs fine.Can't always fly up a hill at a 100mph.Kinda reminds me of my old Tri-Power,either you stay out of it or nail it.

Kinda sounds like a transmission or torque converter issue. Next time disregard the boost gauges and look at the RPM gauge and see what it'* doing.

When was the last tune up with plugs and wires?

Don't know just got the car a little over a week ago.RPM'* do jump around a little and it acts like it'* trying to downshift out of Overdrive. It'* like it balancing on a edge and don't know which side it want to bo on,Giddy up and go or just go.If that makes any sense.

Change the plugs, test the wires and coils https://www.gmforum.com/t278818/, replace the fuel filter and air filter. See if this continues, then I would recommend a tranny fluid drain and filter change - don't do a flush. If it still happens after that, then I'm still leaning towards the torque converter.

Curious. Why not a flush?
Thanks,
Bill

A flush can break things loose and cause more problems then they fix. Best to just drain and refill. If the fluid is really bad, do it again in a few months.

Thanks for the quick reply. I flushed at 78,000 and again at 127,000. No problems with trans so far. Am I on the right track with this maintainence?

That should be fine. But no need to flush all the time. Fluid and filter is just fine.