What times did your series 1 run? (14s?)
With 300kg less and 15bhp more you should beat them. But probably only from a rolling start, if the guy can launch it you'll be beaten off the line, but come back fairly quickly.
I'm not running big bhp. Only just gone upto 1 bar and about 275bhp.
I came from an MG montego turbo that had about 240bhp and a fastest 1/4 of 13.9. My standard Gtir felt slower, but I never dragged it totally standard. With 246bhp and full weight it did 13.08 and with 50kg less weight, smaller wheels and tyres and the same power it did a 12.7.