Hello All! New to the Forum here

(I've already searched this with no result)

When I accelerate to 15mph and stop at a stop light, the rpms will dip low (sometimes stall) and then return to a perfect idle in 2 seconds. Engine response is great. Engine was rebuilt 500 miles ago, every sensor replaced at same time, everything on the engine is new. Ran flawlessly until I went to install a transmission temp sensor/gauge; while hooking up my new temp gauge (the + simply run off the ignition), i accidentally shorted the circuit at the source of the gauge. So I replaced the gauge fuse I blew in the fuse interior panel and checked every other fuse in the interior panel and engine bay. I thought I was good to go. Now the tachometer won't give a reading upon startup until I rev it to 1200 rpms and it jumps to life. I've completely removed transmission temp gauge from the system, with no difference.

So can anyone please help me diagnose this issue? I'm guessing it correlates to what I did, but I'm stumped.

Thanks in advance!