1.7rr and stock springs...need help

[Old Guy with 87 GT]

i was wondering how many guy run stock springs and 1.7s and if you've ever had problems with valve float

.....i just put crane full roller 1.7s on my car ......i replaced the springs with brand new stock ones and had a complete valve job done ,(all tolerances checked and ok)

well my car pulls great up till about 5,500 rpms then just stops like it hits a rev limiter......i was wondering if it could be caused by valve float ......i started having a drop off in power at around 5,500 before the mods ,it used to pull all the way up to 6,000 when i firste got the car but started getting weaker above 5,500 gradually as i drove it ....figuered it was just the valve train getting old ......

well i did the above mentioned mods,i just now got it broke in enough to feel safe winding it up and i discovered it just loses ecceleration at 5,500 just like its hitting rev limtiter....i need to get some input on what could caus this

*related details*
autogage tachometer, my bottem end seems in good shape ,most everything sencor wise has been replaced with in the last year, i have new cap, wires ,plugs and coil....fuel pump and filter are brand new......no other magor mods ....list>2 1/2 full exaust ,no cats,equal lenth headers ,15*timing ,180 thermo, heads shaved .02 and mildly ported (just the exuast side and polished both sides) ,crane 1.7s ,adjust reg (44psi) ,no thermactor or related plumbing.....everything else is stock (including intake and tb)with a speed density computer.........

any insites from the guru's would be appreciated, hell any insights would be appreciated