New good converter worth it?

MOPEkidD-3 said

I got my transmission (904) and torque converter from a guy for super cheap, like $150. He claimed the transmission was rebuilt and the converter is a ~2500 stall TCI unit. I've been driving the car with the new stuff for a little over a year now and while the transmission is mostly fine (flares up when downshifting from 3rd to 2nd at high speed for some reason) the converter slips a lot all the time. I've heard not-so-great things about TCI so I'm not surprised if it is crap but how much extra performance will I get from a nice new converter like PTC? I have a 10.5:1 360 with Magnum heads and small Voodoo cam so it has tons of low-end torque. Also still the stock 2.76:1 rear, hoping to have a 3.91 8 3/4 in the future. My gas mileage sucks at 14 avg. which is way less than I know it can do (only managed 17 on a long trip).

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Take the attached sheet to your converter supplier, filled in with all the information asked for. NO BS on the sheet, as you'll only be fooling yourself.
As it's been said, 2:94 gears and a high stall won't work, and any honest converter supplier will tell you it's really difficult to get a "race type" converter to work well on the street, and vise versa. Go to Randy's ring and pinion website. They have a chart you fill in, and it will give you your engine rpm for a set tire size and diff. ratio. Cruising down the highway at 2700 rpm in high gear with a 3500 stall converter is a bad combo, tons of heat being generated and the converter is 800 rpm below stall speed, slipping and sliding away. Used converters - excellent door stop and not much else, as you don't know what you're getting. Just because the converter stalled at 2500 in another vehicle does not mean it will stall at the same RPM with your combination.
Check your cam spec sheet. They usually will recommend what stall conveter would work well with it. Flaring of the transmission upon shifting could mean a lot of things, burnt clutches, lip seals worn out, bands bad, etc., and it could mean that it's on its' last legs.