Trustworthiness is an emerging concern in the development of Multi-Processor System-on-Chip (MPSoC) systems, which often include Third-Party Intellectual Property (3PIP) cores. Malicious hardware trojans in these 3PIP components can create a plethora of system vulnerabilities. In this paper, we explore an imminent threat that originates from a 3PIP core: architectural state preserving trojans (TASP). We illustrate that a malicious TASP can affect the performance of a core without altering its architectural state, thereby disrupting the availability of on-chip resources in a MPSoC system. We propose three complementary techniques to detect active TASPs in a 3PIP core with overheads of less than 5%.