He said they shouldn't be over 100cm. You are correct I that they should be as short as possible and preferably sourced from the hot pipe. You also don't keep the factory restrictors in the hoses when running a/market controllers, I think you left hem out anyway?
The only others causes to over boosting will be restriction on the exhaust side of the turbo, be it from the exhaust, wastegate or exhaust housing itself. I would look at wastegate or dump pipe. I'm not sure how well the factory turbo holds boost up top but if its anything like the s13 t25g it can only hold 10-11 psi up top but to do this it will spike up to 16-18 psi and the small wheels just aren't efficient enough. I would suspect the small wheels in your factory turbo could be much the same cenario. Don't forget different intake temps from ambient air temp can and does effect boost pressures, ie: cooleder air usually causes slight boost spiking, especially during cold winter nights. Probably not so much of an issue for you this time of year.
Cheers.