This is a good question. the smaller piston corvette type installed increase 1-2 but not 3 or fourth
the best is the one that starts from the front first and thas upping the line pressure which can be installed at a service at a trans specialist. its best to leave the car overnight so the trans guy can go in the area with out scolding his hands. i know i have been there for 25 years. some times the valve gets stuck and is difficult to remove. the boost valve and a stronger line presure spring will firm uo rather than crash your shifts and cause you to see a chiro every time you go to 1-2. i installed a kit for this person with a hot vp i upgraded is two times because in his opinion it was not strong enough he liked it so you could sping your wheels in second when the shift occurs. if he knew that the band that applies second is located by a steel plug in the case which slots into the strap of the band and believe me the hole gets oval after a while.
