Tramission prom 1994 camaro z28, bought in october, guy said he just had a rebuild on the trans and put a quick shift in it, yesterday started acting funny,its a 4l60e automatic transmission , wont shift out of first unless i let off the gas, then runs fine down the highway, unless i step on it to pass someone, then it windes out, any suggestions??

Take it to a transmission shop that has a Tech 2 scanner. The tech 2 scanner will not only scan the transmission but can also recalibrate the shift points. Other reason to why it wont shift under WOT it low transmission fluid pressure so check the fluid level and have a pressure test done on the line.
The 4L60E is a great transmission but there are some things that don't work well with them like some shift kits. The ECM is program the shift points which get's messed up if done wrong. best upgrade on the 4L60E was to swap out the servos for corvette servos or after market performance one's all for under $100.00 and in most case better then a after market shift kit.
Good luck and hope this help. take care not to burn up the transmission.