So i have a 95 Gt that is a stock and automatic car and just did some work thats required after so many miles are put on the car. Currently the car is sitting with 96k miles and replaced the harmonic balancer at 90k when it went out. Just replaced the water pump less than 200 miles ago and now since i've replaced that i have no power after 4000 rpms it will pull fine up to then but when its in the 4000-5500 range it just stays there and car loses the pull and wont shift out like it use to. However if i manually shift it thru the gears it shifts,still no power...and this wasnt the case before the water pump went out,now when you get on it,it throws a check engine light for about 10-15 seconds and it goes away. Has anyone experienced this problem before or have any knowledge on the cause?