... what can I do to improve the power?...
---Relearn driving & gain new habits. It'll never respond like a carbureted 302 or 351, it'll very seldomly light up the tires when you put your foot under the hood.
---I'd say start with tuning the fuel delivery. Set the TPS to about .02v higher than the lowest suggested. Run quality oil with a minimum of .01% Alkyl Zinc (now called ZDDP). Cut out the catalytic converter and install 2x Y pipes into a quad pipe for custom header unless someone has found a header to fit the application and scab the V8 headers from the junk yard and a high-flow muffler like a new 6" Cherry Bomb moved closer to the exhaust manifold... or about 18" minimum, behind the hottest part of the exhaust and then 1/4" larger ID pipe from muffler back. Check that all sensors are within their ranges.
---Maybe a different stall torque converter if you want pep. 3:03 gearing? A trans flush and fill and a good, high flow, quality filter. Screw
K&N and Fram. Flow is either sacrificed for particulate filtering or vice versa between those two. ATP racing application all the way... or Baldwin where available. Motorcraft would even do well in the high-flow/racing application.
---Cold air intake. AC-Delco had the best over-all grades in a private, individual test performed by a fireman about 8 years ago on air filters (I hate GM/Delco so it must be true if I am saying it... lol).
---Clean up your electrical. Test wires from one end to the other for resistance and replace wires one at a time if need be. Get rid of steel grounds and make a copper loop, tying in fuse box and battery, around the frame using 10 gauge wire and tap all ground wires to the 10 gauge at the closest point, leaving yourself about 8" for future crimps/repairs.
---Flush the cooling system and all other fluids. Vehicles are supposed to be flushed every 2 seasons if not every two years. They're like the carpet in your house. If you don't clean it once in a while, you take in all the pollutants that are wiped on your carpet and over time, they'll choke &/or poison you.
---Run a quality racing oil. Penn Grade, Kendal, Redline. Camshaft companies like Shnieder, Erson, etc have their own oils as well. Stay away from shelf oil and you'll do just fine... especially Rotella, which regardless of what they say with this new "fleet" term, is no longer for gasoline engines. They do not have an S rating, they are not for gasoline engines. They have a C rating, therefor they are only for diesels. Your final warning is the disclaimer from both the oil company and the API.
Refer to your owner’s manual for type of oil to use.
http://www.apicj-4.org/2009_ENGINE_OIL_GUIDE.pdf
---Don't use it. Don't use SM API on anything older than a 2006 unless you add you rown zinc-alkaline (Alkyl-zinc ... or ZDDP as it's now commonly referred to)
---Replace those crappy teflon wheel bearings with steel ones and deal with the hardly noticeable road noise.
---Use suggested greases in specified areas and never mix grease bases. Silicon Synthetic grease mixed with a Molly based conventional grease (molly in the u-joint originally) being the worst, can destroy u-joint needle bearings, when operated under hard load, in as few as 100 miles.
---Keep air oil & fuel filters clean.
---Losing weight is on the list too
~edit~
-Forgot...
---Move that TFI to a place other than the distributor.