need help, 91 camaro rs 3.1

for awhile now my camaro has been stalling out on me when i press on the brakes...when i press the brakes my rpm's bounce a little high and then they drop and it stalls out, while im driving, in park, or in neutral...i've changed egr valve, iac valve, pcv valve, fuel filter and pump, i have changed vacuum hoses...its been doing this for 3 weeks now and i dont know what else to do...and the engine does not give me any codes...i want to thank you guys in advance for any help you give me......

good possiblity the check valve on the brake booster vacuum line is caput.

ill check that out...thnx