Last year I noticed a "ticking" starting at about 1700 rpm with just a little bit of throttle and posted here about it. Originally, I suspected the valves, but that didn't quite make sense because it wasn't there at idle, just the normal valve clatter. I then concluded, with some suggestions here, that it was probably an exhaust gasket leak and ordered a set of exhaust gaskets. A couple of weeks ago, after soaking the exhaust manifold studs with PB Blaster and the miracle ATF/Acetone mixture for a few days, I attempted to remove the manifold and change the gaskets. All the nuts or studs came loose, except one snapped (I discovered it was already cracked half-way, so it wasn't my fault, but still no consolation). That really put a damper on things and I still couldn't budge the manifold; maybe there are other bolts underneath that need to be loosened. Anyway, I tightened everything up again and hoped one less stud wouldn't make a lot of difference since the manifold is such a solid cast iron lump.

So, driving around the last couple of days I made another observation. This "ticking" is a steady rhythm and does not seem to change pitch the same as the engine as the revs go up and down as I accelerate and the transmission changes gears. What else could it be? Could it be the fuel pump?