New controller issue

[swell1960]

Hello, long time observer, first time poster. I have a 2004 48volt club car DS plain Jane no IQ, no regen, purchased cheap, have rehabbed it over the last year, just a list of the electrical upgrades I have done, new Powertron battery pack, new F-R switch, new RTS MCOR, stock motor rebuilt, new solenoid, 2 gauge cables. The cart was a 12mph now a 17-18 mph! All done by observing, reading and wrenching myself. OBC has been completely bypassed and have a Lester on board charger. Now my problem if anyone can help, The cart was running great, but I had an issue on long rides after about a 30- 45 minutes the cart would loose power 50% at least and I would have to limp back home, after this happened a couple times I determined it was the last thing I hadn't replaced the controller. so I ordered a curtis style 1204m-5305 48volt 5-0k unit, installed it today and the cart now hesitates 1-3 seconds when pedal is pushed then moves slowly top speed only 11mph at best. I was meticulous about marking wiring so I could put it back correctly but cant figure it out. I checked battery pack each one 8.5-9volts, checked voltage at controller 51-52 volts,is my new controller bad? did I order the right one? any help will be much appreciated!