As was already said, if you know how to launch the car at all (maybe a 2.1 or so 60') it should run around a 14.2 assuming you have your KR under control (which you should with headers). And as was also already said, rockers would REALLY wake it up with the headers and all. Then with some good weather, a smaller pulley, and a good launch, 13'* may not be unachievable. I believe I could've pulled a 14.2 or maybe even quicker in my moms SSEi with a good launch (and I'm pretty good at launching FWD cars) and a little tuning, but she, without any tuning, and a 2.299 60', pulled a 14.681 @ 94.90, and supposedly she let off the gas before the end, so that seems pretty good to me. And here car has essentially the same mods as yours except it has rockers instead of headers (gives about the same power gain). So based on that, I would say that is why your car should be capable of running a 14.2.
1990 Maroon Grand Prix STE McLaren 3.1 Intercooled Turbo, 14.695 @ 94.49 on 12psi before cam/heads/etc.
1990 Bright Red Grand Prix McLaren 3.1 Intercooled Turbo, 14.819 @ 92.72, 189whp
1999 Grand Prix GT 9.75:1|K&N|160 tstat|No Ubend/Cat/Res|UD Pulleys|Ported M90/TB/Heads|XPZ|2.55"|Pacesetters|Stage 2 I/C. 12.442 @ 112.78
2000 Blue Bonneville SSEi Supercharged Gutted Airbox|K&N|3.4"|1.9'*|WP Pulley|Custom DHP|180*stat|41932'*|No Cat. 14.681 @ 94.80
2002 Dark Cherry Grand Prix GTP Supercharged & Intercooled
12.084 @ 114.38 w/1.743 60', 315.6whp, Fastest Stock Cam M90 GTP!
NOW XP CAMMED, 340.6whp with XP, stock heads, Gen 3 M90, 11.984 @ 115.84 w/1.750 60'!
Most HP Stock Heads Gen 3 M90 GTP!
2004 Red Monte SS Supercharged K&N|3.4 Pulley|1.9'*|180*stat|41919 plugs|3" dp|No cat/ubend|DHP|Shift Kit. 14.2 @ 98
GOT BOOST??? Friends dont let friends drive stock!