97 new owner

Picked one up, a 97 with 113K, 5 speed, manual steering, A/C thats it. I calculated about 32 on the way home, 100 miles all highway, the A/C makes a rapid clicking/rattling noise but goes away above ~1200 rpms, sounds like the compressor, but WTF could it be, a bad compressor would make noise all the time, the AC works great. The temp goes real low on the highway, that may be affecting the mileage, that or the O2 is going out.
There is a code for the EGR vsv, I checked it and its wide open all the time, I can pull a vac at the source and the valve moves, I guess its stuck open, but also the vac source at the air box doesn't seem to be enough the valve when the throttle is opened.
Does this engine have hyd or solid lifters?
I get manual tomorrow so that should clear things up. I wish I could find a bunch of these little things cheap, so easy to fix, cheap and reliable.