Can anyone who's installed this kit, preferably on a 2.5l, give it a good recommendation? Would installing this make much of a difference?

Thanks,
Mike

The "shift correction kit" is a good investment for the 125 transmission, but it is not what most people consider a 'shift kit'. It does make the shifts quicker, more firm and consistant but don't expect it to chirp the tires when it hits 3rd gear.
The transgo kit is available from :
http://www.bulkpart.com/cgi-bin/miva?Merchant2/merchant.mv+Screen=PROD&Product_Code=49932&Category_Code=125sk for $17.95, you will need to also get a side cover gasket for $0.63 part #49130, pan gasket for $0.83 part #49140 and a filter for $4.62 part #49921. The total is $24.03 instead of the Fiero Store's $44.95.

What exactly is the kit, besides the gasket and filter?

Some spacers for the 2/3 apply piston, some new springs and spacers for the valve body and a new spring for the governor. It was not hard to install in my van, just messy because some of the fluid missed the bucket. You have to pull the bottom pan to put in the 2/3 piston spacers and the new filter and pull the side pan and valve body for the other stuff. The governor is the unit where the speed sensor is and it is the easiest part of the kit. It helped my transmission because it was slipping into 2nd and 3rd really bad and with the Caddy v8, it just could not hold up to full throttle upshifts. After I got the shift kit installed, the torque converter went bad and I ended up replacing the tranny anyway Since the new tranny is working pretty good, I am not messing with it for a while longer.

The TransGo is an excellent kit. Superior also makes a good kit.
I had the TransGo in my original trans and have it in my new trans.
It helps the shifts go quicker and also prevents the torque converter from losing fluid during hard cornering.

This explains what the kit does and why:

http://www.txchange.com/transgo.htm

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