Odd problem, 2.2 only revs to 5, odd exhaust note Options

[Spart]

I have a 95 Celica GT liftback, 5 spd. The car is normally rev limited at 6.2k, and you can tell when it hits the limiter because it "bounces" off.

So today after driving away from work to go to lunch, I did a U turn because I forgot my wallet, as I sometimes do. And as I sometimes do, I decided to floor it, being out in the middle of nowhere. And then a strange sensation, the car just sort of stopped revving at 5k. And I noticed that the exhaust note was "funny." A little metallic sounding, whereas normally it's just grumbly. There doesn't seem to be any loss of power until you get it up to around 5k.

Quick look under the hood, nothing seems off. CEL isn't on.

I'm at a loss.

[Spart]

to do a compression test start the car and let it warm up to operating temp. Then shut it off and pull the efi fuse in the main fuse box under the hood. Then pull one spark plug at a time and screw the compression tester into the spark plug hole. now hold the throttle wide open and crank the car over a few times. Then read the pressure and write it down. Do the same for the other 3 cylinders. The BGB says it should be around 178 psi and a minimum of 142psi. you should not have a difference in psi over 10%. Example highest cyl is 178psi lowest should not be lower than 160psi.

Cool, but what about a leak down test? Are there any special procedures for this? For example, with a Ford 4.6 I was working on, you had to have the cylinder at a few degrees past or before TDC before you hooked the air compressor up to it.

Just FYI, earlier I checked the spark plug wires and they all look brand new, as they should since I replaced them about 12,000 miles back. Replaced spark plugs, cap and rotor at the same time. Also, I checked the antifreeze and it doesn't seem to be contaminated.

Also, I don't have issues with loosing antifreeze or overheating so I don't think that this is a head gasket issue...