I'm wondering if I don't have a fuel pressure problem, either from a partially-clogged fuel filter or a worn out fuel pump. When I accelerate moderately from stop, the car feels smooth and powerful. When I get on it however, it feels like its holding back, especially in a passing situation; winding up somewhat slowly, not commensurate with a car with almost 300 hp. Also, a few weeks ago I got on it hard off the line, and it almost stalled and threw codes for lean left and right banks. It hasn't done it since, but I've been babying it a bit.

I have an appointment to get the fuel filter changed next week (original with 60,000 miles), but I'm wondering if this is a symptom of the fuel pump about to go bad. In the interim, is there a fairly straightforward way to check fuel pressure in the system?

 

Fuel pressure could be possibe, but that one can be measured by putting a pressure meter on the fuel rail. Another option would be a bad coil, that gives a similar effect, difficulty here is that you don't get any codes, so you don't know which cylinder is bad. It wouldn't hurt to check/read your plugs as well. Another option might be a MAF issue. These are the most common issues I can think off my head considering your symptoms.

 

See Gus' page here to check the fuel pressure at the Schrader valve on the fuel rail: JagRepair.com - Jaguar Repair Information Resource
One note: You need to use a Ford (smaller size Schrader valve) adapter for your fuel pressure gauge.

You may also want to check that your throttle percentage goes over the full range to 0 to 100% with an OBDII reader..it could be your throttle cable is out of adjustment, though that in itself will not cause the lean problem.

 

Thanks to everyone who offered such useful suggestions. I hadn't had a chance to replace the part-throttle plastic breather hose that I had "temporarily" repaired with electrical. Sure enough, the tape had allowed the piece to partially come apart, so I grabbed the new hose and put it on (after breaking the fitting on the valve cover trying to remove the old house). Horrible experience. Anyway I repaired my handiwork with some silicone, let it set up, and went out to see if there was any change (my test was very scientific; I put it in Sport mode, and floored it on an entrance to a local highway. It wound to over 6,000 RPM in every gear before I let up near 80 mph. One moment like this is almost worth the amount of maintenance these cars require.

By the way, how do you get those "Norma" connectors off? Serious PIA.