Those turbo plus kits were actually a waste of money IMHO as the only thing it really did was add more ignition retard safety (to prevent detonation even more) when boosted too high IF detonation occurs. The main reason cars with turbo plus were faster was because the boost was then manually adjusted during the kits install but anyone can do that w/o that kit anyway. The stock ignition system will also retard timing if knock is sensed so the kit was nothing more than pure overkill, a waste of money.
I've previously experiemented with a bleed valve and tossed it out as it created uncontrolled over-boost where it'd go way too far, too fast on full accell and not only was that bad, it didn't help performance enough to make it worthwhile. I'd advise not going over 13.5psi max boost as that's the max allowable adjustment in the T-Plus kits instructions and much more than that is likely to shorten your engines life, especially if it's already a tired old, high mileage beasty with piston slap (knocking at idle). Do be sure to use a good calibrated boost guage if and when adjusting boost, not that POS on the dash.