Chevrolet Repair: loss of power, oil pressure gauge, filter cap

Question
My 98 4.3 l 5 speed p/u has about 88000miles and has been a great truck. Lately it loses power when climbing steep grades at highway speed (4th gear 55 mph). When this happens the engine begins missing and running very rough, and the engine light blinks about 15 times and then stays on for a couple of days. In-town driving seems OK but I've noticed some peculiar fluctuations of the oil pressure gauge on occasion. It has a new cat., air filter, cap and rotor and got a major tune up at 66000miles.

Answer
When the check engine light flashes it indicates that the engine is misfiring enough to cause catalytic convertor damage. You'll need to use a scanner to determine which codes are stored and perform the related diagnostics. Most likely a misfire is causing the problem...spark plug, plug wire, cap, rotor, or injectors are just some of the possible causes.